The invention proposes a method and an apparatus for testing a magnetic field of a coil. The method comprises applying an alternating current to the coil to generate an alternating magnetic field; measuring simultaneously the induced electromotive potential at a plurality of positions in the alternating magnetic field; and collecting and processing signals of the induced electromotive potential so as to obtain said coil's magnetic field distribution. The apparatus comprises probes positioned in said alternating magnetic field to generate the induced electromotive potential; a multi-channel data acquisition card for collecting the signals of the potential; and a processor for processing the collected signals to obtain said coil's magnetic field distribution. The method and the apparatus eliminate the interference by the magnetic field of the earth by testing the coil's alternating magnetic field to improve test accuracy and to improve the testing efficiency by multi-channel acquisition of the test signals.