According to the GNSS carrier phase pseudorange observation equation,the double difference equation of the carrier phase of multimode GNSS double antenna baseline vector rotation is given.By using the carrier phase information of the dual antenna during the rotation,the double difference value of the integer ambiguity of the multimode GNSS dual antenna carrier phase is obtained.Through GNSS satellite ephemeris data and the location of GNSS double antenna,the unit vector from the satellite to GNSS receiver antenna is calculated.The heading angle of the GNSS dualantenna baseline vector is calculated by using the double differenced carrier phase equation and the coordinate transformation of the GNSS double antenna baseline vector rotation.The multimode GNSS dual antenna rotation test shows that the accuracy of heading angle determined by this algorithm is higher than that of commercial software,and the directional speed is fast.