Abstract: Agriculture is the foundation of our national economy, and the level of agricultural mechanization is an important symbol of the development level of agricultural productive forces. With the rapid development of modern agricultural mechanization technology, hydraulic technology has been widely used in large and medium-sized agricultural machinery, but the hydraulic failure is concealed, the cause is complex, and the search and maintenance is difficult, which seriously affects the stability and safety of agricultural machinery operation. In view of these problems, on the basis of summarizing the common faults and diagnosis techniques in the working process of hydraulic system, the appropriate maintenance methods are put forward according to the fault causes.