In view of the small diameter of fiber optic gyro inclinometer application demand, an attitude algorithms of continuous survey system based on an improved attitude heading reference system was proposed. The algorithm fuses aerospace inertial navigation model and petroleum logging parameters, including two optical fiber gyroscopes and three accelerometers to form inertial measurement unit (IMU). According to inertial navigation principle, an improved attitude heading reference system is extended to the wellbore survey field. Using the output data of IMU after the algorithm calculated, the attitude angles of dynamic continuous logging is calculated by the quaternion method. The algorithm decreases one optical fiber gyroscope than general IMU, thus reduces the volume, weight and cost. The simulation results show that the algorithm meet the demand of oil well logging technology.