These years have witnessed the growing impact of worms that target mobile phones, which attracts more and more research interests and applicable focuses. Traditionally, SI model is used to analyze the dynamics of the worm propagation, which adopts the ldquorandom surferrdquo hypothesis. However, the contact social network of a mobile phone population is static and fixed in a short propagation period, which means the traditional SI model will overestimate the worm propagation dynamics. This paper will explore the dynamics of SI model based on a static contact network using social network analysis method. Theoretic analysis and simulated experiments show that the traditional SI model overestimates worm propagation dynamics even in the worst contact network structure.