The strontium atomic optical clock in space experiences changes in the geomagnetic field during its orbit of amplitudes of approximately 80 μT. By introducing changes in the external magnetic field of the same magnitude， the influence of the changing magnetic field on the loading of cold atoms from the magneto-optical trap to the optical lattice of the space optical clock is observed. The influence of the changing geomagnetic field on the detection of clock transitions is theoretically analyzed， and the need for magnetic field stability is investigated. The magnetic field of the space environment is simulated by rotating a permanent magnet. Furthermore， a three-dimensional fluxgate probe is used for real-time detection， and an active compensation system is designed to compensate the external magnetic field synchronously. Because the magnetic field in the central area of the magnetic optical trap of the space optical clock fluctuates by a sub-μT magnitude， it can meet the compensation and control requirements of the space optical clock with respect to the magnetic field.