This paper designed a small MEMS SINS/GNSS navigation system based on ARM processor. The analog output of MEMS gyro/ accelerometer was sampling by AD chip and delivered to ARM processor. GNSS chip provided speed and position information of the system. SINS/GNSS loose couple Kalman filter was achieved and the attitude angle was corrected. A sequential Kalman filter method was used to further correct azimuth angle which suffer from poor observability. After dynamic ground experiment, compared with relative high precision SINS, roll and pitch error were less than 0.5 degree, azimuth error was less than 0.9 degree The combined navigation system achieved in this work enables the use of less accurate IMU.