Most of the existing schemes of auxiliary equipment with lower limbs have some problems,such as large variation of center of gravity,poor lifting stability,difficult motion control and insufficient layout flexibility.Therefore, a new humanoid stair climbing gait motion robot was designed.The translation mechanism and the lifting mechanism were combined to realize the stepped motion trajectory.The core components,key functional principles and main mechanical characteristics were studied; the feasibility of the lifting mechanism design of the combination of double shear fork structure and screw drive was verified.The results show that the mechanism can adapt to the stair scene with step elevation height of 160 mm to 180 mm and plane length of more than 290 mm,and has good load ladder climbing function.