Abstract: The preprint platforms have been given the important mission of fighting academic monopoly and realizing academic freedom from the beginning of theirs birth, and they have gradually established a "decentralized" scientific communication system in the course of development. First, this study combs the previous literature. The results show that:(1) Although researchers have done a certain amount of research on the preprint platforms, these studies focus on the function construction and influence of the preprint platforms. (2) Previous research did not pay attention to the impact of the preprint platforms on the scientific communication system. Secondly, this study uses case analysis, combined with communication and management theories to analyze the impact of the preprint platforms on the scientific communication system, in order to expand the theoretical horizon of related research directions. This study selected bioRxiv, medRxiv, SSRN, Sciencepaper Online and others as the research object, and analyzed the positive effects of the preprint platforms on the scientific communication system. The results show that:(1) In the traditional scientific communication system, journals serve as the information dissemination center, integrating a large amount of scientific communication information, creating a centralized scientific communication system. The emergence of the preprint platforms broke this rule, imitating social media, and designed a mechanism for the participation of scientific researchers with equal powers. This form of communication improves the transparency of scientific communication. (2) In the traditional scientific communication system, journals as "gatekeepers" uphold the power of screening, processing and presenting scientific information. The preprint platforms divide the gatekeeping power of journals, allowing every researcher to participate in the review with the help of social sharing functions. This increases the amount of feedback in scientific communication and enhances the interactivity of researchers. (3) The preprint platforms embed the informally communicated information into the literature and transmit it to the journals. This method integrates the communication channels of formal communication and informal communication, blurs the boundary between formal communication and informal communication. (4) In the traditional scientific communication system, formal communication is mainly spread through journals or conferences. However, due to the strong uncertainty in the review cycle of journals or conferences (as short as a few days, as long as several months or even years), scientific information creators have a high degree of time lag in receiving feedback. The appearance of the preprint platforms reduce the time lag in scientific communication and makes scientific communication more immediate. Third, this study also analyzes the negative impact of the preprint platforms on the scientific communication system. The results show that: (1) During the occurrence of “COVID-19”, many low-quality articles were published on the preprint platforms, which were widely disseminated through the platforms. This reduces the trust between individuals in scientific communication, forming an opinion climate of lack of trust, and may even create a crisis of trust. (2) For researchers with low information discrimination ability, it is difficult to distinguish between low-quality and high-quality preprints from the massive amount of information, to determine whether the data conforms to the objective facts. For scientific researchers with high information discrimination ability, they can use the preprint platforms to quickly capture cutting-edge information and improve their own scientific research awareness in a relatively short period of time. This may increase the differences between individuals in scientific communication. (3) The quantitative mechanism of the preprint platforms (introduction of hot rankings) may lead to scientific exchanges only for the pursuit of new topics, not for knowledge sharing. (4) The quantitative mechanism of the preprint platforms may also prevent some unpopular disciplines from obtaining attention resources, making it difficult to enter the policy agenda. Finally, this study also believes that the future development of the preprint platforms need to deal with three contradictions: (1) The contradiction between immediacy and controlling the quality of information. (2) The contradiction between capitalization and scientific publicity. (3) Contradiction with the interests of the journal (the right of first publication). The preprint platforms have changed the way of scientific communication in many disciplines and strengthened the communication between researchers. However, preprint platforms still have shortcomings and need constant repairs to return to the essence of scientific communication.