Becoming members of social networking websites is now one of the most popular on-line activities. Although the number of users has been growing exponentially in social network sites (SNS), some SNSs are facing a financial crisis and might be shut down in the near future. Therefore, understand users’ incentives to switch to another SNS has great influence on operators’ business performance. The study extended “Push-Pull” migratory theory to explain the switching behaviors of users in SNS. Structural equation modeling (SEM) was applied to analyze data collected from 618 users by questionnaire survey. The result shows that pull effects have the greatest influence on users’ switching behaviors, followed by push effects. As a result, the study suggests that operators should satisfy users’ pursuit of freshness, and carefully examine whether their services could address users’ needs of socializing and entertainment