In order to overcome the difficulty of fault detection and clearing in the use and maintenance of a type of rocket mine-sweeping vehicle, the operation principle of fire-control system, the fault characteristics, fault parameters and fault distribution are studied. Furthermore, the fault detection instrument based on embedded system is developed. It consists of hardware and software. The hardware includes of embedded micro-controller STC5A60S2, keyword and highlight LED I/O, LCD, memory circuit, connector-adapter and dedicated connection cable. The dual CPU cooperative technology is also used in the hardware platform. The application software is developed with expert system principle, it runs in two modes of simplified and expert mode. In simple working mode, fire-control fault detection and substitute are performed. However, in expert mode, all the function of system testing, system substitute, fault-clear wizard and parameter management is accomplished. Meanwhile the state machine programming technology is introduced in the software. The instrument brings new ideas how to deduce expert repair in the field, and it has practical value.