Abstract: In order to study the torsional stiffness of push-rod teeth transmission with pin gear and influencing factors of the torsional stiffness, the formulas for calculating the meshing force and torsional stiffness were derived based on the deformation coordination method. By means of an example analysis, the variation law of the meshing force between the push-rod tooth and the pin, the variation law of the torsional stiffness of push-rod teeth transmission with pin gear were analyzed. The influence of the structural parameters of push-rod teeth transmission with pin gear on the torsional stiffness was discussed. The research results show that: there is the least meshing forces at the top and the root of the push-rod tooth profile, and there is the largest meshing force in the middle of the tooth profile; the torsional stiffness of push rod teeth transmission with pin gear fluctuates little; the eccentricity of generator and the number of pins have great influence on the torsional stiffness; the radius of pin and the radius of pin gear have little influence on the torsional stiffness; the influence of generator ’s radius on the torsional stiffness can be neglected. The research results can provide theoretical basis for tooth profile modification and parameter selection of the push-rod teeth transmission with pin gear.