The fault diagnosis of SF6 gas-insulated equipment is of great significance for ensuring the safety of power grid. Studies have shown that accurate detection of SO2F2, a characteristic decomposition product of SF6, helps to determine the early latent faults of equipment. To this end, this paper studies the SO2F2 detection technology based on laser spectroscopy, analyzes the infrared spectral characteristics of SO2F2 and its coexisting gases, and finds that SO2F2 has a strong absorption peak at 2763 cm−1 and is not interfered by its coexisting gases; a laser absorption spectroscopy experimental platform is built using a 3619 nm ICL laser to carry out quantitative detection research on trace SO2F2. The results show that in the concentration range of 0–600 ppm, the system response of the direct absorption spectroscopy is 0.782 mV/ppm, the repeatability error is 2.267 ppm, and the detection limit is 3.94 ppm; the harmonic modulation method can comprehensively improve the detection performance, with a system response of 11.433 mV/ppm, a repeatability error of 0.977 ppm, and a detection limit of 357.56 ppb. The research results provide theoretical and technical support for on-site charged detection of SO2F2.