The invention discloses an automatic water draining device. The automatic water draining device comprises a valve body, an inner cylinder is arranged in the valve body and vertically arranged, the outer wall of the inner cylinder is covered with an annular coil rack, and a coil used for producing a magnetic field is wound on the coil rack; a sewer pipe is arranged on the upper portion of the valvebody, downwards stretches into the inner cylinder and communicates with the inner cylinder; and a spring jacking sealing structure and a magnetic adsorption water draining structure are arranged in the valve body. The invention further discloses a fuel filter which adopts the automatic water draining device and has an automatic water draining function and a using method thereof. According to theautomatic water draining device, the fuel filter using the automatic water draining device and the using method, water can be automatically drained in time, the condition that a water collecting cavity is filled with water is avoided, the service life of a filter element is prolonged, the condition that an engine is damaged due to the fact that fuel oil contains water is prevented, the using costof the fuel filter with the automatic water draining function and a motor vehicle is reduced, and the maintenance operation frequency is decreased.