With the continuous improvement of power grid voltage level, the requirement of equipment condition detection is also increasing. The existing detection technology of dissolved gas in oil is difficult to meet the early monitoring and warning of equipment failure of high voltage level. The technology of oil and gas separation and gas enrichment based on headspace degassing principle was studied. An automatic plasma gas chromatograph with nitrogen as carrier gas was developed. Through integrated design and intelligent control, the instrument realizes automatic analysis of transformer oil. The equipment can reduce the manual operation error and environmental interference in the detection process, with high detection precision and low detection limit. It has a good detection effect on oil samples with low concentration gas content, and has a good application prospect in the analysis and diagnosis of early faults of high voltage oil filling equipment.