Abstract: The method of using spiral coil to measuring ring electromagnetic field generated by hypervelocity impact process is detailed in this paper. The shielding effect of the coil on outside interference magnetic field was analyzed. Under the experimental condition that the spherical LY12 aluminum projectile with hypervelocity of 6.2 km/s impacted LY12 aluminum target plate, the variation of magnetic field intensity with time was measured by using coil and its integral circuit. Test results showed that the time of transient electromagnetic fields generated by plasma lasted about 1ms and the most significant value was 15 μT.