Abstract: Many studies have proved that source credibility has a significant positive impact on the propagation effect. However, does science popularization in the era of social media also follow this rule? Traditional Persuasion Communication researches focus on all aspects of the complete communication path that may cause attitude changes, including source, information, channel, and destination. In recent years, researchers have paid more and more attention to understanding how the audience completes information decision-making behavior from the perspective of social cognition, emphasizing that persuasion is a process and that different information processing methods change their attitudes and behaviors. Based on the Heuristic-Systematic Model theory from the socio-cognitive perspective, this study samples 743 science short videos from 20 representative accounts on the “Douyin” platform. In the content-coding stage, researchers first establish the coding category table, and then three coders encode the samples. In the data analysis stage, the reliability of the coding results is tested first, and then the hypotheses of the heuristic cue and systematic cue and their sub-hypotheses are verified by the parameter test method. To verify the effect mechanism, factor analysis is used to calculate the argument richness score, heuristic cue score, and systematic cue score of each sample, then the sample grouping of argument richness and consistency is carried out with the median, and finally, correlation analysis and regression analysis are used to verify whether there is bias, additivity, or attenuation effect. The results of content analysis show: 1) Authoritative sources can’t play a better propagation effect and have a significant negative impact, reversing the positive cognition of authoritative sources in the traditional media environment. Science communication has transferred from the "top-down" mode to the "equal dialogue" mode. 2) The concentration of content, narrative mode, the use of music, and expression mode are important systematic cues that affect the propagation effect of science short videos. Only those science short videos with "temperature" can stimulate emotional resonance. 3)When the evidence provided by the science short video is insufficient, the heuristic cue score is not related to the propagation effect, indicating that there is no bias effect. 4)Under the condition of sufficient evidence provided by the science short video, when the heuristic cue score is congruent with the systematic cue score, the additivity effect of both on the propagation effect is not significant. In contrast, the scores of the two cues are incongruent, and the influence of systematic cues on the propagation effect is more significant than that of heuristic cues, that is, an attenuation effect occurs. It suggests that we should pay attention to the expression and emotional narration in the process of science popularization. However, there are still many imperfections in this study. From the actual samples, there is some uneven distribution of variables, such as music use and expression mode; In addition, because the content analysis is manually encoded, there may make the encoding no objective. These may have a certain impact on the results of statistical analysis. Future research can also include text analysis, such as qualitative analysis and emotional analysis of the comment text in the sample.