In this paper, the influence of surface pitting on the dynamic response of geared system under light surface pitting was studied analytically and experimentally. In previous work, tooth pitting faults were mainly modeled by considering the reduction of the mesh stiffness. The effect of sliding friction was largely ignored. This paper aims to evaluate the contribution of mesh stiffness reduction and change of friction on gear dynamic response introduced by surface pitting faults, especially for incipient pitting. In this work, both the mesh stiffness and the friction are considered in modeling and simulation. Pitting experiments were conducted and the experimental results were compared with analytical simulation. Simulation results indicated that the impact of slide friction is significant during the initial pitting stage. However, for sever pitting, the reduction in mesh stiffness is more critical. It is also shown that the sidebands in pitted gearbox saw obvious increase in both simulation and experimental results.