SG-PSM-200 transformer oil gas photoacoustic spectroscopy online monitoring system is a precision equipment integrating control and measurement analysis technology, mainly used to monitor online the content of fault characteristic gases (H2, CO, CO2, CH4, C2H4, C2H2, C2H6) and micro water dissolved in the oil of oil-immersed high-voltage equipment such as transformers and their growth rate, and to forecast equipment hidden information through fault diagnosis expert system to avoid equipment accidents, reduce major losses and improve the reliability of equipment operation.