Abstract: A spin state readout device of a quantum sensor. The quantum sensor has spin-manipulable electrons. The spin state readout device includes: a pumping unit configured to emit a first laser to the quantum sensor to polarize the electron spin state of the quantum sensor; a probing unit configured to emit a second laser to the quantum sensor to make the spin-polarized quantum sensor in an excited state; a signal receiving unit configured to receive fluorescence photons emitted from the quantum sensor and convert optical signals into electrical signals; and a timing unit coupled to the probing unit and the signal receiving unit and configured to time an excited state lifetime of the quantum sensor. The spin state readout device of the quantum sensor provided can reduce spin state reading errors caused by laser power drifts, system signal collection efficiency drifts and the like.