The mesh stiffness calculation and load distribution among teeth of helical gear are the basis of its dynamics analysis and strength calculation. Aiming at the accuracy of approximate replacement method of mesh stiffness of helical gear, the quasi-static elastic model of helical gear was established based on the change rule of contact length, quasi-parabolic model of single tooth mesh stiffness per unit of contact length and ISO6336-1 standard, and a comparative study was conducted with the approximate replacement method based on quasi-static rigid model and ISO6336-1 standard. The results showed that the results calculated by quasi-static elastic model were in good agreement with the ISO standard results when the ratio of the minimum stiffness to the maximum stiffness of single tooth α,k, is 0.55, and the errors of the quasi-static rigid model and ISO standard were large. Based on the quasi-static elastic model, the effects of geometric parameters and broken teeth failure on meshing stiffness and load distribution coefficient of helical gear were analyzed and discussed, which provided a basis for the study of fault dynamics.