To solve the problem of power compensator for lift-fan UAV, this paper focuses on the design and analysis of the power compensator system during the landing process of lift-fan UAV. Firstly, the longitudinal state equation of lift-fan UAV was established and simplified. And then, the basic control structure of power compensator was built. Finally, aiming at the characteristic of lift-fan UAV, the power compensator system integrating various compensators was established, and this system was simulated and analyzed. The result indicates that the simulation response time in the power compensator system at the constant speedis shorter than the other.However, the damping which can cause oscillation is deficiency. In order to alleviate the oscillation, subsequently, the longitudinal overloading is analyzed according to the specific characteristics of lift-fan UAV, and the effect of power compensation with spoiler is also researched. The results show that modes of aircraft are goodand effectively increase the tracking precision of the attitude angle of flight path angle.