Abstract: In recent years, China’s automobile has developed rapidly with the trend of booming production and sales of 20 million units every year, and the gearbox structure has developed from manual to automatic; Including CVT,AT,AMT,DSG etc.The automatic transmission brings us more comfortable driving fun, avoids the trouble that the manual transmission needs to lift and step on the clutch frequently in the past, and avoids the disharmonious behavior of many drivers and passengers who are not used to lifting and stepping on the clutch and shifting gears.With the vigorous development of social economy, customers’ awareness of maintenance and repair of gearbox has gradually improved, but there are still some abnormal phenomena such as jitter in actual use, such as stuck shift, poor shift, unable shift and other faults, which seriously affect the driving feeling.According to my superficial understanding, this paper analyzes the causes of abnormal sound of automatic transmission.