We performed research on a quadrotor with tiltable-rotors,which has full controllability over the position and orientation,and established its dynamics system.To handle the system's strong nonlinearity problem,a nonlinear separation strategy was utilized to decompose the nonlinear system into a linear dynamic subsystem and a nonlinear static system by constructing intermediate control.Subsequently,linear quadratic regulator with small calculation and easy hardware implementation was designed only for linear dynamic subsystem while real control including tilting angle and motor speed was mapped from intermediate control by calculating the input nonlinear static subsystem.Simulation results illustrate that LQR flight controller based on nonlinear separation strategy not only performs well under a stable control,but also in independently tracking control of position and orientation.