Abstract: To realize knowledge base of intelligent pilot-s assistant system during the full flight course, hierarchical architecture based on task decomposition was adopted. The hierarchical knowledge base was proposed: task-judging level, field-judging level and aiding-making level. Cooperative team combat mission of fighter aircraft was analyzed emphatically. And 14 sub-tasks were defined according to the flight phase, situation and objective. The sub-task, attack air target beyond visual range, was studied. The sub-task was disjointed by 5 fields on the time dimension or spatial dimension. Modules architecture of the hierarchical knowledge base was established by the expert system software tool C language integrated production system(CLIPS). The effectiveness and the feasibility of hierarchical architecture are demonstrated by the distributed real-time simulation system.