In this paper, we adopt switching technology of double satellites navigation mode based on BeiDou-2 (BD2) and Global Position System (GPS), design GNSS/MIMU integrated navigation system based on TMS320C6747. The designed system is not affected by the possible transient invalidation of GNSS. The hardware design of system is completed. The navigation switching technology is analyzed when GNSS signal is disturbed, and the Kalman filter of system is designed, what's more, the precision of system during navigation mode switching period is held through MIMU. Thus we realize seamless switching of navigation mode. We adopt integrated navigation system based on BD2, GPS and low-cost IMU, which increases the stability of system when the signal of satellites navigation system is disturbed. Additionally, we provide results and system details from several experiments to further prove the effectiveness of the integrated navigation system.