The aerodynamic configuration of the tiltrotor aircraft was constantly changed during the tilting transition process, and the aerodynamic characteristics had been strongly nonlinear characteristics. Aiming at the complex states of continuous tilting transition for the tiltrotor aircraft, the grid system suitable for the simulation of the continuous tilting transition for the tiltrotor aircraft had been established through the moving embedded grid and local coordinate system theory in this paper，and based on the RANS equation, a CFD method suitable for unsteady flow field analysis with strongly nonlinear aerodynamic characteristics was established. The method was used to simulating the aerodynamic characteristics of the continuous tilt transition for a certain type tiltrotor aircraft from helicopter mode to fixed wing mode. The results showed that the aerodynamic characteristics of the rotors and the airframe had the same trend with the increase of the rotor tilt angle for different tilt transition time（t=1s and t=2s）; As the rotor tilt angle increase, the lift coefficient of airframe was first increases and then decreases, and achieved the maximum value near 40°, which was about 30% increase compared to the initial state and level flight; As the rotor tilt angle, collective pitch angle and forward flight speed linearly increase, the rotor tension coefficient and its vertical component gradually decreased.; With the linear increase of the rotor tilt angle and forward flight speed, the total lift of the tiltrotor aircraft could be kept near the target value by using a suitable nonlinear variation curve of the collective pitch angle.