In the field of EMC testing, there is a lack of magnetic field immunity evaluation methods suitable for digital magnetic isolators. To solve this problem, the following studies were carried out. Firstly, the working principle of the digital magnetic isolator is studied. Based on the principle of electromagnetic compatibility and IEC standards, a set of evaluation methods for the magnetic field immunity of the digital magnetic isolator based on the GTEM small chamber method is established. The test system was built, the circuit board was designed, the test seat method was used to solve the problems of incorrect direction and insufficient strength of the magnetic field coupling in the disturbance rejection test, two failure modes and criteria of level fluctuation, and fixed 0/1 were defined, and the comparison table for structural analysis was designed. Second, the case of the GL1200P digital magnetic isolator was verified to verify the feasibility of the test method, and the device’s antidisturbance failure sensitive frequency was determined to be 113 MHz, and the rating was 400 V/m—C. The case proves that this method can evaluate the immunity of digital magnetic isolators.