Abstract: A device for measuring a scalar magnetic field based on pulsed optical pumping, including: a first laser, a first isolator, a first ?/2 waveplate, a first polarizing beam splitter, a first coupler, a first spectrum analyzer, a reflector, an atomic sensor probe, a second ?/2 waveplate, a second polarizing beam splitter, a first photoelectric converter, a second photoelectric converter, a data acquisition system, a second laser, a second isolator, an acousto-optic modulator, a third ?/2 waveplate, a third polarizing beam splitter, a second fiber coupler, a second spectrum analyzer, a ?/4 waveplate and a beam expander. Two planar reflectors are respectively arranged at two sides of the atomic sensor probe and face towards the atomic sensor probe, and are arranged parallel to the pump beam input to the atomic sensor probe.