According to the trouble feature of hydraulic system, using the principles of Artificial Intelligence(AI) Expert System and the design method of object orientation, the Troubleshooting Expert System of Agricultural Machinery Hydraulic System (AMHSTES) was developed by means of Borland C++ languages on the computer, which solves the contradiction that the supply is unable to meet the demand for Troubleshooting experts. The “rule + fault tree” model of knowledge representation, the mutual knowledge gaining form, the forward inference tactics and the CF model of inaccurate reasoning were adopted in AMHSTES. Furthermore, the system has the function of explaining troubleshooting process. It can greatly raise the efficiency and precise rate of Hydraulic System Troubleshooting. 