A new pattern of inertial navigation system was introduced which was called roll-isolated strap-down inertial navigation system and used in spinning projectile.By supporting the inertial instrument cluster on the stabilization platform which was isolated from the spin, IMU was isolated from high rate rolling, thus realizing inertial guidance based on MEMS.Roll-isolation prevents the saturation of the roll gyro by high spin rate, and this greatly reduces the measurement errors arising from gyro scale factor and alignment uncertainties.Navigation based on MEMS has the advantage of small size, light weight, low cost, low power, high reliability, large measure range and high degree of integration thus particularly suitable for precision-guided munitions.