Abstract: This paper presents an experimental study of water unlocking stimulation mechanism on surfactant fracturing fluid based on the measurements of surface tension, contact angle, gas-phase permeabilities and desorption of nitrogen on synthetic coal samples. The coking coal in Liulin zone of Hedong coal field was used as testing object in this study. Active water and surfactant fracturing fluids were used as testing liquids in this study. Results show that the surfactant fracturing fluid(1.5%KCl+0.05%AN) reduces the surface tension of active water fracturing fluid(1.5%KCl) and increases the wettabil-ity of active water fracturing fluid to coal reservoir; the surfactant fracturing fluid reduces the capillary pressure of fluid in coal pore to make the fracturing fluid easily access into the coalbed methane reservoir; the surfactant fracturing fluid can re-duce the water blocking damage rates of coal reservoirs by about 40%; and the surfactant fracturing fluid inhibits the occur-rence of water blocking damage efficiently. Regarding to the coalbed methane reservoir, the surfactant fracturing fluid has the stimulation effect. It is concluded that the surfactant fracturing fluid increases the gas-phase permeabilities at bound wa-ter saturation of coal reservoir, thus realizing the permeability increasing, and the surfactant fracturing fluid reduces the crit-ical diameter of coalbed methane production, thus realizing the desorption increasing.