Abstract: The automatic transmission oil pump is one of the vibration-and-noise excitation sources of the whole transmission. Based on the analysis of noise generation mechanism and corresponding countermeasures, the oil channels and relief grooves were optimized. Flow pulsation analysis was performed by means of fluid simulation software. A verification test was conducted with noise-testing software. The results show that the structures of oil channels and relief grooves affect flow pulsation and further the noise level. It is verified that the oil pump noise is greatly reduced after structural optimization, realizing the target of noise optimization.