The work and operation conditions of key components of mechanical press such as，the balancer，pneumatic stretching pad，clutch and brakes,as well as their sealing requirement to large pneumatic Y sealing rings were analyzed.Through analyzing the installation requirement and sealing performance of domestic large pneumatic Yrings,the seal structure of the key components of mechanical press were optimized.The reliability of the domestic large Y sealing rings is further verified through their practical application in the mechanical presses.