The magnetic field coil is the core part of the magnetic field system of the nuclear magnetic resonance gyroscope (NMRG). It is also the core component of the inert gas magnetic resonance excitation maintenance and active magnetic compensation. The coupling of transverse magnetic field coil has great influence on the accuracy of magnetic compensation and magnetic resonance excitation. Therefore, it is very important to calibrate the coupling of the transverse magnetic field coil. In order to solve the above mentioned problems, a coupling calibration method of transverse magnetic field coil based on the built-in magnetometer of NMRG is proposed. The correctness and feasibility of this method are verified by theoretical simulation and experimental design. The experimental results show that the proposed coupling calibration method is used to calibrate the X-to-Y-axis coupling and Y-to-X-axis coupling, with values of 1.86% and 3.11%, respectively. By rotating the coil to change the assembly angle, it is shown that the measurement results are not affected by the assembly error when the rotation angle is small. By calibrating a total of 5 coils from the same batch, the coil with less coupling is selected for assembly according to the results, which provides a basis for the selection of NMRG coil.