Strap-down inertial measurement unit (SIMU) is composed of three gyroscopes and three accelerometers, however there often exists space synchronization error and time synchronization error caused by the limitation of installation and the phase frequency characteristics of its inertial device. Space synchronization error, called lever-arm error or size effect error, is navigation error which is caused by the misalignment of three accelerometers measurement points. Time synchronization error (also called time delay error) is caused by difference between phase frequency characteristics of gyroscope and accelerometer. Under the condition of the non-orthogonal installation of the accelerometer, it establishes mathematical model of the lever-arm error and it can get parameters of the lever-arm by designing a simple experiment method. Aiming at the phase frequency characteristic difference of inertial components, time delay parameters are calculated through establishing the relationship between the accelerometer time delay and navigation accelerometer speed error, and the compensation are directly achieved with the inertial velocity updating algorithm. Then, verify the rationality of theoretical analysis by means of the turntable experiment. At last, the final conclusion is provided.