Abstract: Aiming at the demand of small delay measurement of photoelastic modulator (PEM) in high-precision optical rotation detection, a high frequency and small delay PEM scheme for optical rotation detection is proposed.COMSOL（COMSOL Multiphysics） finite element simulation was used to simulate the vibration mode analysis and size determination of a 120 kHz PEM in standing wave mode, and to design and process high-frequency small-delay PEM samples. It is verified by experiments, and the amplitudes of one to four octave signals are extracted by FPGA（Field Programmable Gate Array） as the main research object, which realizes the automatic calculation of small-delay PEM phase delay amplitude and the measurement of rotation Angle. The experimental results show that the PEM frequency of the measuring system is 120.32 kHz, the average phase delay amplitude is 0.11 rad, and the repeatability is 0.0007. The amplitude of phase delay is 2.9 times smaller than that of traditional single PEM, which has great practical significance for weak and high-precision optical rotation detection.