Abstract: To meet the measurement requirements in aspects such as oil and gas resource exploration and dynamic monitoring of water environment, and to improve the measurement accuracy and timeliness of dissolved hydrocarbons in water, a rapid measurement method for dissolved methane in water is studied. Methane saturated water is prepared using high-purity methane gas standard substance, and the methane saturation time is optimized. The results show that after 60 minutes of ventilation, methane in the water completely reachs the saturated state. A series of standard solutions of methane in water are prepared by diluting saturated methane water to establish the calibration curve. The analytical effects of direct injection - gas chromatography and headspace injection - gas chromatography are compared. The results show that when headspace injection is used to analyze dissolved methane in water, both the repeatability and sensitivity are superior to those of direct injection. The measurement conditions of the headspace sampler and gas chromatograph are optimized, and a rapid determination method for dissolved methane in water is established. The optimized analytical conditions are as follows: gas-liquid equilibrium temperature of 70℃, gas-liquid equilibrium time of 20 min, injection port temperature of 200℃, column oven temperature of 80℃, and FID detector temperature of 230℃. The dissolved methane samples in water are measured by headspace sampler - gas chromatograph, The analysis results show that within the range of 1.16～11.6 mg/L, the standard curve of methane presents a first-order linear correlation, with a correlation degree of R² = 0.9997, and the detection limit of the method is 4.6μg/L. This method can achieve quantitative analysis of dissolved methane in water. The preparation time of the standard solution is short, and the analysis time is only 5 minutes. It has the advantages of being rapid, accurate and easy to operate.