The invention discloses a method for detecting diamond color center spin in a sensing way based on a microwave phase modulation spectroscopy technology. The method comprises the following steps: (1) symmetrically installing a microwave transmitting end (4) and a microwave receiving end (5) at the inner side of a diamagnetic circular ring (8), wherein the microwave transmitting end (4) is connected with a microwave source, and the microwave receiving end (5) is connected with a data acquisition port of a field programmable gate array (FPGA) or a signal input end of an oscilloscope card, or the microwave receiving end (5) is respectively connected with the signal input end of the oscilloscope card and the data acquisition port of the FPGA by a port divider. According to the method, resonance signals of diamond color center atoms are detected in combination of the microwave phase modulation spectroscopy technology, the electronic energy level is excited by using laser, an external magnetic field is scanned, and the change of microwave signals is detected by means of an absorptive action of a diamond color center ground state energy level for a microwave field, so that color center spin information is read. The detection method is simple and convenient and high in accuracy, eliminates the complexity and instability of a light path, and increases the signal-to-noise ratio of atomic magnetic resonance.