Abstract: Based on the simulation methods of TCA and LTCA,a new approach to the gear geometric surface design for increasing the contact ratio is proposed in the paper to supersede the traditional method which regards the contact path as being perpendicular to the root cone.We purpose to develop the design method for high contact ratio by means of sloping the contact path.The designed gear set has lower transmission error under load,reasonable load distribution and excellent meshing behavior.The experiments of the tooth root stress and noise testing have proved that the method is efficient for designing the high contact ratio gear set,and has some advantages of dynamic behavior and strength.