For the organizational specialty of a virtual enterprise, the enterprise faces more complicated risk management problems than those in the traditional enterprise. So, to analyze the main affecting factors about the risk and to assess deeply the level of risk management for a virtual enterprise have their important and realistic significance. Based on the aspect of life cycle, this paper divides the cycle of a virtual enterprise into four periods, which are recognition period, construction period, operation period, and termination period. After that, this paper analyzes the possible risks that occur in each period and establishes a set of risk indicator system. According to these, the paper constructs a risk assessment model based on the fuzzy mathematic theory, then adopts this model to evaluate the project risks of virtual enterprise, and testifies its effectiveness through an example finally.