Abstract: The continuous cooling transformation curve of undercooled austenite of C70S6 non-quenched and tempered steel was reasonably measured. The quality of the connecting rod of fracture splitting of C70S6 non-quenched and tempered steel was analyzed by mechanical property test, metallographic examination and fatigue performance test. The results show that uniform and stable microstructure after rolling could be obtained by high-temperature diffusion heating and controlled rolling and controlled cooling in the rolling process. Controlling the cooling rate after forging could make the ferrite proportion in the microstructure of the connecting rod far below 10%, and effectively prevented the occurrence of abnormal microstructure such as martensite. The physical and chemical properties and fatigue life test results of the final C70S6 non-quenched and tempered steel connecting rod of fracture splitting could meet the operation requirement.