In terms of the evolution of complex dynamics in the dissemination of public opinion, a dynamic evolution model was proposed based on transmission dynamics. Firstly, the models of public opinion and its evolution were constructed and the static solution was obtained through equation transformation. Secondly, the Fokker-Planck equation was introduced to analyze the asymptotic behavior of public opinion evolution, getting the steady-state solution and solving it. In that case, the correlation between the complex network and the model was built and the experiment objective of simulation research was put forward. Finally, through the simulation analysis of the public opinion evolution model and the public opinion model with the Fokker-Planck equation, and the empirical analysis of real micro-blog public opinion data, the essence of the dissemination and evolution of public opinion in the complex network was studied. The results show that the asymptotic behavior of public opinion network evolution is consistent with the distribution of degrees and the connection way of network public opinion dissemination is influenced by nodes. The model can describe the dynamic behavior in the formation and evolution of micro-blog public opinion network.