Gas-insulation equipment is a key equipment for urban power grids and high-voltage power transmission. The chemical properties of SF₆ gas are usually very stable, but when latent faults such as discharge or overheating occur inside the equipment, SF₆ will decompose to produce toxic and corrosive gases such as SO₂. SO₂ indicates whether there is an arc or spark discharge fault in the equipment, and the SO₂ content produced is closely related to the severity of the internal defects of the equipment. Electrochemical sensing, semiconductor sensing and gas chromatography are the main traditional methods for detecting SF₆ decomposition products. However, they generally have disadvantages such as low sensitivity, large cross-interference, short life or long response time. Photoacoustic spectroscopy uses the sensed absorption energy to achieve gas detection and is a background-free and highly selective trace gas detection solution. SO₂ gas has absorption in both mid-infrared and ultraviolet bands, ultraviolet Light-Emitting Diode (LED) has the characteristics of low cost, simple structure, low power consumption and good stability. Using photoacoustic spectroscopy and low-cost ultraviolet LED excitation source, a photoacoustic SO₂ sensor with high sensitivity, high reliability and miniaturization for SF₆ decomposition product in high-pressure gas insulation equipment is designed and implemented. An integrated photoacoustic SO₂ sensor was designed, which mainly includes an excitation source, a lens group, a photoacoustic cell, a Micro-Electro-Mechanical System (MEMS) microphone, a gas pressure sensor, a window, an air inlet valve, an air outlet valve, an inlet and an outlet. The photoacoustic cell is a device for holding the gas to be measured, and the photoacoustic effect is generated here. The reasonable design of the photoacoustic cell structure is conducive to the improvement of the photoacoustic signal and the signal-to-noise ratio. The cell constant of the photoacoustic cell working in the non-resonance mode is inversely proportional to the square of the radius of the photoacoustic tube and the modulation frequency of the incident excitation light. The gas chamber volume and dimensions of the sensor are only 10.2 mL and 40 mm×40 mm×36 mm. This miniaturized design makes the sensor have the advantages of low gas consumption, simple structure and portability. Photoacoustic gas sensors are affected by gas pressure. The gas pressure range in the gas chamber of gas-insulation equipment is approximately 0.25~0.4 MPa. The photoacoustic signal is related to the degree of collision between the gas molecules to be measured. Theoretically, when the gas to be measured is in a state of non-saturated absorption and the gas concentration and the incident excitation power are constant, the high gas pressure will increase the energy absorbed by the gas molecules to be measured, thereby stimulating a stronger photoacoustic signal. Theoretical analysis and simulation verified the promoting effect of high pressure on photoacoustic excitation under SF₆ background gas. The integrated pressure sensor is used to display the gas pressure value in real-time, and the influence of gas pressure on the photoacoustic response, background signal, noise and detection limit is tested. Real-time monitoring of SO₂ concentration generated by SF₆ decomposition to achieve accurate analysis and early warning of latent fault types and severity within gas-insulation equipment. Taking advantage of the positive correlation between photoacoustic excitation and gas pressure, the high sensitivity of the photoacoustic SO₂ sensor in a high pressure environment is achieved. The performance of the photoacoustic SO₂ sensor is tested under a gas pressure environment of 0.4 MPa. Detection limit is one of the most important factors in evaluating a sensing system. The results show that the detection limit reaches 56 ppb with an averaging time is 100 s, which provides a powerful preventive measure for the safe and stable operation of high-pressure gas insulation equipment.