Abstract: A method of the stress influencing matrix is proposed for calculating bending stress courses on teeth root of the helical gears.The stress influencing matrix of mesh nodes on the surface of the gear teeth and on nodes of its contact lines is established by using 2-D interpolation and then is multiplied by the load distributing matrix on the nodes.Therefore,the bending stress courses on the gear teeth root are obtained.By means of generating the flexibility matrix on the gear teeth root the finite element calculation of this method is only needed once to obtain the distributing conditions of loads on the working surface of the gear teeth and distributing conditions of the bending stresses on root surface of the gear teeth for whole meshing period.The calculated results are compared with the experimental data.It is proved that the method of the stress influencing matrix is as accurate as the finite element method,but can save computer memory and calculating time to a great extent.