Abstract: Based on the analysis of four typical hydraulic system failures caused by temperature change, the authors elaborated that the "difference in the coeffcient of thermal expansion between the hydraulic oil and steel" is the primary cause. Meanwhile, the authors also analyzed the specifc cause and gave the corresponding treatment in detail to each specifc failure, combined with the analysis on the reasonability of treatment measures or suggestions for the use of equipment. This paper aims at providing the useful reference to the relevant personnel who use hydraulic equipments and handle hydraulic failures.