The rockets are being developed toward the long range and precision guide, the guidance device is the core of the rockets. Based on the strapdown inertial navigation technology and Kalman filtering technique, a miniature strapdown inertial navigation/GPS integrated navigation system has been developed by using MEMS gyro, quartz flexible accelerometer, high dynamic GPS receiver and high speed navigation computer. The integrated navigation system has the features of small size, high accuracy and low cost. The experimental results showed that the inertial navigation system could satisfy the requirements of the guidance of the range extended rockets.