On the basis of the M-B fractal theory, a geometric model and contact mechanical model of the tooth surface contact mode were analyzed. According to the energy dissipation mechanism of tangential contact damping, a tangential contact damping model of tooth surface considering variable friction under dry friction condition was established by introducing the correction coefficient of tooth surface. First, obtained the load and tangential damping of a micro-convex body, and then the contact load and tangential contact damping of the tooth surface are obtained by integrating on the tooth surface. It was shown that the tangential contact damping of tooth surface is affected by various parameters including roughness amplitude, fractal dimension, curvature radius of tooth surface, normal contact load and tangential normal load ratio. The simulation results show that the tangential contact damping gradually increases when the normal contact load, friction coefficient, curvature radius of driving wheel and roughness amplitude increase. The tangential contact damping on the tooth surface increased with the increase in the tangential normal load ratio. When the tangential normal load ratio is 0.09, the tangential contact damping of the tooth surface reached a maximum, and then decreased with the increase of the tangential normal load ratio. The change in the tooth surface tangential contact damping with the fractal dimension is similar to the change in the tangential normal load ratio, which also increased and then decreased. When the fractal dimension is approximately 1.64, the tangential contact damping of the tooth surface reached the maximum. The tangential contact damping of tooth surface increases with the increase of modulus, transmission ratio and the number of teeth of the driving gear, and the number of teeth and modulus have a great influence on it, while the influence of transmission ratio is relatively weak.