Hydraulic support is an important mechanical equipment in fully mechanized mining face. The reliability of hydraulic support is very important for the safety of coal mine production. The ZY6400 / 21/45 type hydraulic support was taken as an example, the maximum stress of the hydraulic support as the optimization target, and the average trouble-free operating time as the reliability index. The thickness of the main structural steel plate of the shield beam under the greatest force was optimized and obtained excellent steel plate thickness. Practice showed that the reliability of the optimized hydraulic support was significantly improved, which guaranteed the safe mining.