The present gear hob is used to replace worm, and the front angle of hob tip blade is fixed at 7° and up, which is an important reason for the excessive tooth shape error. Through analysis of the analytical theory of hob modelling calculation, and a regression to itself with involute gear hob geometric characteristics, use of selecting such formed envelope instead of Archimedes spiral surface as the blade profile, the optimal points before the round angle hob design, again through the optimization of design parameters, process parameters, etc., the modelling of hob accuracy was made and increased by more than ten times. Not only the new blade mouth can achieve high precision of tooth profile, still can keep the tooth profile accuracy after resharpening. The “radial relief grinding” adopted by the hob increases the grinding angle, and extends the service life of cutter.