Abstract: Take the large modulus wind power annular gear with hardening and tempering as the research object, three different concentrations of PAG water-based quenching for comparison were used and the effect of mechanical properties whether to pre-opening teeth or not before heat treatment was studied.The results show that, when the hardness of the quenched body fluctuates within 1%, to pre-opening teeth or not has little effect on the mechanical properties and metallographic structure of parts.The concentration of quenching liquid has little effect on the hardness of parts after quenching.The tensile strength and yield strength show a parabolic trend with the increase of quenching liquid concentration.The metallographic structure is the same at 8% and 10% concentration, when at 8.5% quenching liquid concentration, the pre-opening teeth hardened and tempered piece's metallographic structure of tooth root is better than that of the no pre-opening teeth.