Mission reliability is an important presentation of the comprehensive combat effectiveness of UAV system. In this paper, the research work is mainly focused on the design method of flight test for mission reliability verification of UAV system. By developing the mission failure criteria, sample size determination method, evaluation of the mathematical model, mission profile design and integrated test implementation process, a mission reliability verification method has been formed. The proper design method would provide the basis of and the guidance for the mission reliability verification of the UAV system and enables a feasibility verification through examples.