The electrical system of the construction machinery usually works on circumstance of high temperature, serious vibration and shock, dust pollution as well as electromagnetic interference, so the electrical system is very likely to go wrong while compared with other systems, for example working attachment, under chassis and so on. In view of this, an advanced fault test device, with application of embedded equipment and virtual technology, is developed in this work. The function and implementation of software are illustrated. The device is composed of PDA, cradle and CF-bus data acquisition card. It can test and diagnose the circuit and electronic component fault. Furthermore it stores the data and upload data to server simultaneously for further diagnosis and processing of repair and maintenance expert. The fault test device may be utilized in fault diagnosis of electrical system and components of engineering vehicles, subsequently improve the maintenance and diagnosis capability for the electrical system.