The current situation of the large forging equipment in China and the gap with the world level were outlined. Based on the analytical study on  the characteristics of the housing construction of the large close-die forging press, the plan of choosing C\|plate housing for 800 MN large close-die forging press was put forward. The mechanical design of C-plate pre-stressing combination frame was improved, the innovation to the manufacturing technique was made, and the strength, rigidity and  fatigue life time for C-plate frame were analyzed and optimized.