SQUID magnetic sensor

The invention provides a superconducting quantum interference device magnetic sensor. The magnetic sensor comprises the components of a first superconducting quantum interference device; an under-feedback circuit which is used for amplifying an electric signal that is output from the first superconducting quantum interference device according to a preset proportion and performs inverse feedback to the first superconducting quantum interference device, so that the electric signal which is output from the first superconducting quantum interference device after feedback is output according to a periodical single valued characteristic and furthermore the electric signal that is output at the ending time of each magnetic flux sub-change-period included in an outer magnetic flux hops from a peak value to a working zero point at starting of the magnetic flux sub-change-period; and a signal processing unit which is used for determining the amplitude of the digital waveform signal of each magnetic flux sub-change-period according to the direction of each hop edge in the received electric signal and generating the digital waveform signal, and overlapping the received electric signal with the generated digital waveform. The superconducting quantum interference device magnetic sensor can perform measurement in the range of a plurality of magnetic flux sub-change-periods, and furthermore effectively prolongs measurement time and enlarges measurement range.