Since the tiltrotor aircraft needs to switch configurations among helicopter mode， transition mode， and fixed-wing mode within its flight envelope， and its dynamic characteristics vary significantly under different configurations， it is necessary to design control laws for different configurations to ensure satisfactory control performance across all three modes. To address this issue， a six-degree-of-freedom nonlinear model of the tiltrotor aircraft considering center-of-mass movement is established. An integrated control law with a unified structure is designed， and normalized weighting coefficients are introduced for the transition mode. Taking the longitudinal control channel as an example， mathematical simulation results show that the designed integrated control law achieves satisfactory control accuracy in all three modes and demonstrates good robustness under both model uncertainties and control law parameter variations.