In order to improve navigation precision of laser strap-down inertial system in high-dynamic environment, the high order error model including quadratic errors and size effect errors of accelerometers was established, and reasonable incentive path of errors was designed. Velocity errors were used as the observational vectors, the turntable test data were identified by the system-level identification method, and the compensation effects of common error model and high order error model were compared: in 900 s dynamic navigation process, the eastern velocity error declined from 15 m/s to 3 m/s, and the northern velocity error declined from 10 m/s to 2 m/s, which indicates the high order error model based on the system-level identification can improve navigation precision effectively.