The fluxgate magnetometer described in this paper has been widely used to measure ship magnetic fields and other objects. Due to the complexity of its power supply circuit，there are some shortcomings such as large volume and small battery capacity. Aiming at the above problems，the charging and discharging parts of the power supply circuit and the battery capacity have been redesigned and improved，which can reduce the volume and make it convenient to use in the outfield. Besides，it can also be maintained and replaced quickly and timely，and the integration and overall performance of the instrument，and the stability and efficiency of the ship magnetic field measurement have been improved.