Abstract: Based on the working principle of the magnetometer, a new magnetoresistive magnetometer is designed for improving its noise performance, with improved magnetometer probe structure and the mode of AC-coupled and closed loop to eliminate the impact of the randomly oriented magnetic domains and to stabilize circuit working state. The test results for the key performance show that the noise power spectral density at 1 Hz is 38 pT/√Hz. In addition, the magnetoresistive magnetometer has a small size and a light weight, so it is easy to install, and it can especially meet the requirements of small satellites.