The utility model relates to the field of refueling equipment. Particularly, the whole oil transportation process is completed in a closed environment; therefore, oil gas leakage is effectively prevented, and use safety is guaranteed. The device comprises a pre-filter, a fine filter and a main flow meter which are connected in sequence, a branch prying pipeline is arranged at an outlet of the mainflow meter, the branch prying pipeline is communicated with a main pipe reeling device, the main pipe reeling device is communicated with each branch pipe reeling device, and each branch pipe reelingdevice is communicated with an oil gun. Due to the fact that sealing of the whole oil supply process is achieved, it is guaranteed that oil gas and oil liquid leakage does not exist for airtight oilfilling, constant-pressure, quantitative, airtight and unattended automatic oil filling can be achieved in the whole oil filling process, and the automatic oil filling device is particularly suitablefor various unattended automatic oil filling applications.