The dissemination of disinformation has become a thorny issue in the era of social media, and knowledge can play a crucial role in tackling this problem. However, currently more research interest lies in the disinformation dissemination model, but ignores the interaction between disinformation and knowledge in the diffusion process. In order to explore the evolutionary path and stable strategy for the competitive dissemination between disinformation and knowledge on social media, an evolutionary game model based on social capital theory is proposed in this paper. By model solving and numerical simulation, the initial dissemination willingness, the disinformation infection probability, the knowledge infection probability, and the knowledge penetration probability are demonstrated to be important factors affecting the game equilibrium in the competitive dissemination process of disinformation and knowledge. Moreover, some countermeasures and suggestions for the governance of disinformation are put forward. The present study reveals the dynamic mechanism of social media users disseminating disinformation and knowledge, and is expected to promote the formation of a cleaner cyberspace.