In order to ensure the reliability and safety of the aviation equipment, improve the maintenance and support ability of the system, the system testability has been put forward higher requirements.By analyzing the testability problem of the system, a testability objective function model is established, and a method for selecting testability objective of complex aviation equipment is designed by integrating functional importance analysis, risk impact analysis and fault tree analysis techniques.An example analysis of teteability target selection method is carried out through an aviation auxiliary power plant engineering case.The results show that this method can provide engineering design basis for the testability design of aviation complex equipment.