To address the need for high-sensitivity detection of sulfur dioxide （SO₂） concentrations in gas-insulated switchgear （GIS）, this study designs and develops an ultraviolet photoacoustic gas sensor based on an LD-pumped all-solid-state Q-switched laser. The sensor uses a UV laser with a central wavelength of 266 nm and an emission power of up to 36.93 mW as the excitation source for the photoacoustic signal. A non-resonant photoacoustic cell with a volume of only 0.39 mL is employed to amplify weak photoacoustic signals. By detecting these signals, the SO₂ concentration is determined in real time. Through the optimization of key parameters such as modulation frequency, the sensor achieves a detection sensitivity of 286.9 ppb at room temperature and under atmospheric pressure, with a 1-second integration time. Experimental results further demonstrate that the minimum detection limit can reach 9.1 ppb when the integration time is extended to 100 seconds. This photoacoustic detection sensor exhibits high sensitivity, excellent selectivity, and long-term stability, providing efficient and reliable technical support for the early diagnosis of potential GIS equipment faults.