Modeling is the basis of flight control system for unmanned helicopters. In this paper, modes partition method and structure traversal (MPM/ST) method is applied to derive the dynamic models of a small-scale unmanned helicopter, and thereby afford improved accuracy for flight controller design. Increment proportional integral derivative (IPID) controller is applied to each channel to compose the core-dynamic controller, which is designed to follow the hover command of an outer-loop controller. The simulation results showed significant benefits of the proposed approach in flight-control design for unmanned helicopters.