A fault testing device for the electronic instrument of certain type military equipment is developed in this paper. The PC104 bus, modular instrumentation and signal processing technology are integrated in the device. It consists of PC104 bus peripheral system, signal condition circuit, electric distribution cabinet, interface unit, connection cables and peripheral dedicated signal fixture. Based on Windows CE embedded operation system, the application program is implemented with Visual C++ programming language. The device could detect and locate the fault on replaceable unit of modular board and functional block, and could also assist serviceman and technical support personnel in performing quick fault testing and equipment maintenance.