The chain has wide applications in engineering community. The test results and field application show that the main failure mode of the chain is fatigue fracture of the chain plate. The analysis of the chain plate parts P-S-N curve is very important for reliability study of the chain. Due to such good characteristics as time-saving and low cost by the avoided fatigue test,the theoretical P-S-N curve of the chain plate is convenient for application to engineering. The theoretical method of the chain plate parts P-S-N curve is presented the,and the life prediction of the chain is carried out based on the theoretical P-S-N curve of the chain plate. By comparing the analysis results and the conventional design principle of the chain,the feasibility of the proposed theoretical method of the chain plate parts P-S-N curve is verified.