Aiming at the effect on FOG (fiber optical gyro) SINS (strap-down inertial navigation system) caused by shock and vibration in the environment, shock isolation system was designed and analysed. The shock response spectrum was calculated based on the acceleration time-history measured in the shock environment by improved recursive formula and statistical estimate. Then, it was used to guide the parameters design of the shock isolation system. In order to verify the design result, transient dynamic analysis was proposed in ABAQUS. To simulate the shock environment, acceleration time-history was acquired through time-history waveform synthesis and it was used as the base motion in transient dynamic analysis. The result indicates that the shock suffered by the SINS with the designed shock isolation system was declined to an acceptable range, which means the designed shock isolation system was successful in the view of dynamics characteristics. It is significant for the engineering application of FOG SINS.