In order to improve the orientation stability and accuracy of the rotating global navigation satellite system（ GNSS） dual antenna/micro inertial measurement unit（ MIMU） combined system

a relatively minimum geometric dilution of precision（ GDOP） star selection method based on tracking time and altitude angle is proposed. Use the tracking time and altitude angle information of GNSS to eliminate the satellites with poor signal quality stability

and then select the satellite with the smallest GDOP among the candidate satellites

and perform the orientation solution of the rotating GNSS dual antenna/MIMU combined system to determine the true heading.High-precision laser gyro inertial navigation system is used as reference

outdoor static and dynamic tests are carried out on a rotating GNSS dual antenna/MIMU combined system. The test results show that using a satellite with a long tracking time can improve orientation stability of the system

selecting a satellite with a large altitude angle can improve orientation precision of the system

and selecting a satellite with the smallest GDOP can improve orientation precision of the system and real-time performance. Heading angle error of the system is less than 1°（ 1σ） under the unobstructed environment on land

and the horizontal attitude angle error is less than 0. 1 °（ 1σ） .