Aiming at the limitation that the traditional symmetrical gear stress calculation formula cannot be applied to the new asymmetric helical gear, a calculation method of tooth root bending stress of asymmetric involute helical gear are proposed in this paper. According to the meshing principle, the digital tooth surface model of asymmetric involute helical gear is established. The distribution characteristics of tooth root bending stress are analyzed by finite element method, and the relationship between tooth root bending stress and pressure angle is studied. On this basis, the influence coefficient of pressure angle is proposed. Combined with multiple regression analysis, an analytical formula for calculating the bending stress of tooth root without finite element method is proposed. By comparing with the calculated values of the finite element method, the error rate of the theoretical formula is 6.52%, which verifies its accuracy. The research results show that the asymmetric helical gear exhibits excellent tooth root bending bearing capacity under high pressure angle conditions, which provides key theoretical support and calculation tools for the design of high-performance asymmetric gears.