The traditional static fault trees with AND, OR, and Voting gates cannot capture the dynamic behavior of complex computer system failure mechanisms such as sequence dependent events, spares and dynamic redundancy management, and priorities of failure events. In this paper, dynamic fault tree modeling method is applied in complex computer system. This paper starts from dynamic fault tree analysis method and its logic gates. A complex computer system simulation example is given. We establish respectively each model, and then gain system-level dynamic fault tree and modularize this model and analyze other questions. At last, we can draw a conclusion that this model method of this paper analyzes well dynamic behaviors in computer system that combines hardware, software and human reason. (4 pages)