Abstract: Through the study of the measured indicator diagram,three parameters of liquid supply capacity of oil wells have been determined,the uninstalled stroke,unloading ratio and the loading-unloading ratio.The higher the uninstalled stroke and unloading ratio,the lower the fluid supply capacity.The higher the loading-unloading ratio,the higher the fluid supply capacity.Four kinds of factors,inertial load,vibration load,gas and leakage,have bigger influence on the uninstalled stroke and unloading ratio,smaller influence on the loading and unloading ratio.Among these three parameters,the loading-unloading ratio is an indicator to show good liquid supply capacity of oil wells.According to the size of loading-unloading ratio,the liquid supply capacity of oil wells can be divided into four grades.