Addressing the current issues where the positioning accuracy of vehicular Global Navigation Satellite System/Inertial Navigation System (GNSS/INS) integrated navigation equipment utilizing consumer-grade sensors is limited to the meter level, and the low attitude measurement accuracy stemming from significant measurement noise in inertial devices, a Differential Global Navigation Satellite System/Inertial Navigation System (DGNSS/INS) integrated navigation algorithm is proposed. To achieve high-precision positioning and orientation of vehicles, pseudo-range differential mode is used to improve positioning accuracy, and fiber optic Inertial Measurement Unit (IMU) is used to improve attitude angle measurement accuracy, and data fusion of system state equation and measurement equation through Kalman filter are achieved. The results of static and dynamic vehicle tests conducted in urban environments show that the proposed algorithm achieves high-precision positioning and orientation of vehicles.