Based on the analysis of firms’ stochastic adoption behaviour, this paper first points out the necessity to build more practical stochastic models. And then, stochastic evolutionary models are built for substitutable innovation diffusion system. Finally, through the computer simulation of the diffusion models, we can explain the evolutionary characteristics of substitutable technological innovation diffusion and get the corresponding diffusion patterns, which are helpful for firms to adopt an innovation at the optimal occasion, and accelerate the evolution speed of the new technology.