A compact ppb-level SO2 photoacoustic sensor was developed for the application of SF6decomposition detection in electric power systems. The selection of the SO2 target spectrum is discussed in detail in the infrared (IR) and ultraviolet (UV) spectral regions. Based on the result of the spectrum selection, a small-sized UV-band diode-pumped solid-state laser (DPSSL) emitting at 303.6 nm with an output power of 5 mW was developed. A differential photoacoustic cell (PAC) was designed to match the output optical beam, obtain a high Q-factor and reduce the system flow noise in the SF6 buffer gas. The performance of the sensor system was assessed in terms of gas flow rate, linearity and detection sensitivity. A SO2 detection limit (1σ) of 74 ppbv was achieved with a 1-s integration time, which corresponds to a normalized noise equivalent absorption (NNEA) coefficient of 1.15 × 10−9 cm−1WHz-1/2.