This paper researches digital filter,uses IIR digital low pass filter to process the raw output of fiber optic gyroscope.In order to eliminate the noise of high frequency,uses the smoothing filter algorithm process the FOG output after digital low pass filter.Using Matlab tools design the filter parameters,uses fiber optic gyroscope without the filter data for online simulation test,adjustes the amplitude frequency characteristics for the desired goal,and then writes the filter parameters into the fiber optical inertial measurement unit and tests.The test results show that:the angular vibration test verifies the correctness of digital filter parameters,fiber optic gyroscope amplitude frequency characteristic descends 8dB in 68Hz frequency point compared without filter; verifies noise of fiber optic gyroscope could be effectively restrained at vibration conditions in the navigation accuracy test,and then position error of east and north is only 18.64m and 25.16m.