Knowledge diffusion can be accelerated through the network. This paper constructs a knowledge diffusion model of high tech enterprise alliance based on NW small world network to reveal the characteristics of the alliance ’ s knowledge diffusion , and uses MATLAB software for simulation. The study indicates that re duction of characteristic path length of network , increase of network cluster coefficient and improvement of knowledge communication frequency between the members are active measures for promoting knowledge diffu sion of high tech enterprise alliances , enhancing innovation effectiveness and developing knowledge innovation.