Abstract: The theory of technology parasitism points out that parasitism between technologies contributes to the symbiotic development of two or more technologies. The disproportionate growth of sub-technologies in host technology will promote the development of complex technology systems. Host technology with more daughter technologies develops faster than host technology with fewer daughter technologies, and the evolution of host technology is not independent of its associated daughter technologies. In the initial stage of parasitism, the influence of external environment is the external condition of parasitism, and the difference within technology is the internal limit of parasitism, which shows that parasitism is selective. In the growth stage, daughter technology and host technology promote each other and coevolve, indicating that parasitism has reciprocity. In the ascendant phase, subtechnologies alternate parasitism with host technologies, indicating that parasitism involves substitution. In the final effect stage, the sub-technologies is alternately parasitic in host technology shows that parasitism has substitutability. Combined with the general law of technological evolution, "Double S curve" can reflect the evolution law of technology from parasitism to symbiosis from the inside of technology. The theory of technological parasitism should abandon the description of evolutionary phenomena and pay more attention to the explanation of bonding mechanism. In the early stage of innovation management, diversity and foundation should be emphasized, while flexibility and orientation should be emphasized in the middle and late stage.