Installation error in inertial navigation system causes an additional interference acceleration existed in accelerater output and gyros drift in gyros output

which can lead to navigation errors.By analysing systematically from theoretical point of viewing the installation error in strapdown inertial navigation system（SINS）

the system’s error model when there are both position-installing error and angle-installing error is concluded

and the influence on SINS’s accuracy caused by installation error is simulated.The results represent the disadvantages stemming from installation error

and the errors can cause rapid accuracy distortion of SINS which must be compensated.The research can paly a positive role in improving the accuracy in the initial alignment of the gimbaled SINS

and be valuable for engineering application.