A-type locking device is widely used in airborne electronic equipment.The failure to fasten the equipment often occurs during operation，which may affect the mounting reliability of the electronic equipment. We studied the working process and mechanism of the A-type locking device through mechanical analysis and contact-surface analysis，and analyzed the factors that affect the fastening performance. The measures for design improvement were put forward，such as controlling the precision of pre-tension force，improving the angle of fixing and reducing the clearance.The result of simulations and tests showed that the improvement can effectively enhance the structural stiffness and strength of the airborne electronic equipment，and improve the mounting reliability of the equipment.