The utility model provides a differential lubricating system, relates to a lubricating system and aims at solving the problems that the existing differential lubricating system is not perfect and has a poor lubricating effect. According to the differential lubricating system, a semi-axis gear oil stopper is arranged on a semi-axis gear, a plurality of casting holes are formed in a differential front housing, the casting holes are uniformly distributed in an annular array manner by using the center of the front housing as a circle center, a first straight oil groove is formed in the inner wall, in contact with a semi-axis gear adjusting shim, of the differential front housing, a second straight oil groove is formed in the inner wall, in contact with the semi-axis gear adjusting shim, of a differential rear housing, an oil groove is formed in the inner wall, in contact with a spherical shim, of the differential rear housing, oil holes are formed in both the semi-axis gear adjusting shim and the spherical shim, first oil nozzles are arranged outside the casting holes, and lubricating oil enters the differential from the casting holes. The all-dimensional lubrication of the interior of the differential is realized, that all parts are connected in a lubricating manner is ensured, the lubricating effect is excellent, and the reliability is high.