During the period of major emergency crisis, the public opinion often falls into the dilemma of low cost of rumor, untimely falsification, high cost of tracing to the source, and great difficulty in proof. In order to solve the disorder of online public opinion, this paper puts forward the perspective of "blockchain + network public opinion governance", trying to form a technical deterrent to false network information by building a credible and binding deposit mechanism of public opinion. The theoretical knowledge of Stochastic Petri Net is introduced to construct the model of public opinion deposit system of blockchain, and the equilibrium state and efficiency evolution law of each sector of the whole chain are tested through simulation. This paper deepens the academic and industry's understanding of the blockchain public opinion deposit system from three aspects: the best optimization sector, the best efficiency scale and the system adaptive ability, so as to provide important decision support for China's application of blockchain technology to improve the network public opinion governance ability.