Abstract: The error factors and the accuracy evaluation in a magnetic test are closely related to the magnetic testing method, the structure size and the magnetic moment’s magnitude, the internal characteristics of the magnetic distribution in the spacecraft, and the magnetic testing equipment. The near-field analysis is the most classical and effective testing method for determining the magnetic dipole moment of the spacecraft. This paper discusses the system error, the random error factors, and analyzes the accuracy evaluation. To determine the testing errors for the vertical magnetic moment results for medium & large -scale spacecraft, some effective methods & measures are proposed to improve the testing accuracy and the error assessment. Finally, the basic conditions and the evaluation criteria are presented for the comprehensive evaluation of the effectiveness in the magnetic testing process for spacecraft. The estimated range of the magnetic testing errors is obtained for different sizes of spacecraft. The related techniques for the error analysis and the accuracy evaluation in the spacecraft’s magnetic testing process are desirable to improve the precision of the spacecraft magnetic test, and to control the spacecraft magnetism effectively.