To solve the problem of hydraulic system fault location that happens in crane, the methods of multiattribute decision making are researched. Firstly, the hydraulic system was decomposed according to function. Then, the fault trees of different function working states of every subsystem were built. Fault localization of hydraulic system was researched by comprehensive analysis of fault probability, search cost, heuristic search and other factors of the bottom event. Optimal search path of bottom event was confirmed by building decision matrix, normalizing attribute, adopting least square method (LSM) to confirm weighted value of attribute, using ranking method of Technique for Order Preference by Similarity to Ideal Solution(TOPSIS). The application results of a crane with the fault of unable to lift show that the method is effectively and practically.