The utility model provides a locking mechanism for an automatic gear shifter, belongs to the technical field of automobiles and solves the problems that a gear is shifted to gear R and gear P by gear D in the existing automatic gear shifter during running, an automatic transmission is caused to be easily damaged and the like. In the locking mechanism for the automatic gear shifter, the automatic gear shifter comprises an upper support, an operating lever assembly, a rocker arm and a main shaft, wherein the operating lever assembly is connected with the rocker arm through the main shaft; the locking mechanism comprises an electromagnetic valve, and a locking hole and a locking groove which are located in the rocker arm, wherein the electromagnetic valve is fixedly arranged in the upper support, the electromagnetic valve is electrically connected with a brake pedal, the pushrod of the electromagnetic valve stretches out and is embedded in the locking hole when the gear of the automatic gear shifter is at gear P and the brake pedal is released, the pushrod of the electromagnetic valve stretches out and is embedded in the locking groove when the gear of the automatic gear shifter is at gear N and the brake pedal is released, and the pushrod of the electromagnetic valve is retracted when the brake pedal is stepped down. The locking mechanism for the automatic gear shifter has the advantages that the automatic transmission is prevented from being easily damaged, the service life is long and the like.