在法拉第效应中，线偏振光通过加有外磁场的磁光介质时，其光矢量发生了旋转.光的偏振方向旋转的角度与磁场 沿着光波传播方向的分量呈线性正比关系，因此通过测量旋光角度即可得到相应的磁场大小.本实验创新性地提出基于法拉 第磁光效应测量空间磁场的方法，利用了半影法减小测角器的测量误差，更加精准地找到了消光位置.实验测得实验室环境中 空间磁场的磁感应强度B= 0.287 mT，并得到磁偏角大小为θ= 7.688°.与使用磁阻传感器进行测量的数据相比，磁感应强度的 相对误差为ηB = 4.6%，磁偏角的相对误差为ηθ = 9.8%.

The Faraday effect is a kind of phenomenon that may cause the rotation of the optical vector when the linearly polarized light is passing through a magneto-optical medium under the influence of an external magnetic field. The angle of rotation of the polarization direction of the light is linearly proportional to component of the magnetic field along the direction of propagation of the light wave. In this paper，the space magnetic field is measured innovatively with the Faraday magneto-optical effect，it can reduce the measurement error of the goniometer and find the exact position of extinction by using the method of the penumbra. The magnetic induction intensity B = 0. 2876 mT of the magnetic field in the laboratory environment is measured and the magnitude of the magnetic declination is θ = 7.6884°. The relative error of the magnetic induction intensity is ηB = 4.6% and the relative error of the magnetic declination is ηθ = 9.8% compared with the data measured using the magnetoresistive sensor.