Aiming at the vertical plane motion control of autonomous underwater vehicle(AUV) with the influence of residual buoyancy, the vertical motion plane control is divided into forward speed control and depth control. Adopting the mature S plane controller to ensure the stability of speed control, the problem of depth control is selectively solved. By introducing the virtual control, the depth deviation with the influence of residual buoyancy is mapped into the desired pitch angle, which is tracked through the design of pitching controller. The stability analysis shows that the proposed underacuated depth control is stable and robust for the variation of parameter estimation. Finally, the simulation results show that the proposed method is resistible for the influence of residual buoyancy, and the depth control is accurate and robust.