Based on the study of the concept and connotation of prognostics and health management (PHM), the basis of the airborne module build in test (BIT) design and the fault diagnosis system is analyzed. Based on the airborne module and the ground fault inspection system, the detailed frame of the airborne module BIT design and the fault diagnosis system is put forward. Through analysis, summary and simulating, the fault prediction model design idea on the basis of PHM is presented. With airborne module BIT design, fault diagnosis method and process, the theoretical support is provided for on line test, production testability and maintainability of the airborne module.