At present, producing clean gas through anaerobic digestion is one of the main means to treat food waste. As food waste contains sulfur, H₂S gas will inevitably be generated during anaerobic digestion. H₂S gas is inevitably generated during anaerobic digestion due to the presence of sulfur in food wastes. The produced H₂S can lead to corrosion in pipelines and environmental pollution. Thus, it is essential to measure its volume fraction online. Traditional H₂S volume fraction measurement methods, such as methylene blue spectrophotometry, iodometry, and electrochemical methods, involve complex operation, slow measurement speed, and can easily be affected by other gases. In addition, these methods cannot be used to guide the timely adjustment of the working conditions of the desulfurization system. Therefore, we develope an approach combined the ultraviolet absorption spectroscopy and continuous wavelength integration method for the online measurement of H₂S volume fraction. The linear relationship between the characteristic value of the absorption spectrum integration and H₂S volume fraction is obtained by selecting a 210?230 nm band as the characteristic band, with a fitting degree >0.999. To measure the volume fraction of H₂S, we prepare 200×10^-6?1200×10^-6 of H₂S standard gas in a laboratory, and the maximum error of the measured value is 3.1%. Finally, the measurement device is applied to the anaerobic digestion of kitchen wastes, and the field test is conducted. The results demonstrate that the instrument can accurately monitor the change in H₂S volume fraction of biogas during the anaerobic digestion process.