The utility model discloses a light path test device for three-dimensional measurement of a weak
magnetic field, which relates to the technical field of weak
magnetic field measurement and comprises a working circular truncated cone, a first support and a second support are fixed on the working circular truncated cone, and the end of the first support far away from the working circular truncated cone is rotatably connected with a placing plate. The end, away from the working circular truncated cone, of the second support is rotationally connected with an angle adjusting plate, a
magnetic field measuring box is fixed to the angle adjusting plate, an
Arduino development board is fixed into the magnetic field measuring box, a
polarizer and an analyzer are arranged on the two sides of the
Arduino development board respectively, and a
photodiode electrically connected with the
Arduino development board is arranged on the Arduino development board. An aluminized reflecting mirror which rotates in the magnetic field measuring box is arranged on the outer side of the
polarizer or the polarization analyzer, and a
Helmholtz coil is further arranged between the first support and the second support; the equipment can more accurately measure the magnetic
field intensity in the
magneto-optic glass, and avoids the limitation that the
Faraday effect can only enable a
light beam in the same direction as the magnetic field to deflect.