Abstract: The shortcomings of the automatic transmission controlling system and the principle of malfunction engendering were analyzed.The closed-loop controlling method was introduced in this paper.By testing the law of executor’s pressure,the time difference of executor’s working status was calculated,and the time difference was limited in a perfect range by controlling the work time of solenoids,so that the shifting quality was improved and the service life was prolonged.Proved by experiment,this method was scientific and more useful.