Abstract: To mitigate magnetic interference affecting the onboard magnetometer of a Mars probe, an integrated magnetic cleanliness strategy was developed and validated. The strategy incorporated an extended support bracket into the solar array deployment mechanism, replacing traditional deployable booms, to maximize the magnetometer’s separation from spacecraft-generated interference fields. Magnetic dipole moment budgets were specified for each subsystem and major interference source. The sensor layout was optimized; low- and non-magnetic materials were employed; and component structures and wiring were refined to suppress hysteresis and eddy current effects. As a result, the magnetic influence of key components was significantly reduced. Test results showed that the magnetic field at the magnetometer location remained within approximately 1 nT, meeting the measurement accuracy requirements for Martian magnetic fields. This magnetic cleanliness approach serves as a practical reference for the magnetic design of future deep space missions.