The invention discloses a structure for preventing oil mist from overflowing from an oil groove of an electric generator and achieving condensation and deposition. The structure comprises an electric generator rotating shaft and an oil groove sealing cover, wherein a space at the lower part of the electric generator rotating shaft is sealed by the oil groove sealing cover, so that the oil groove for storing lubricating oil is formed. The structure is characterized in that at least one circle of sealing layer is arranged on the outer side face of the intersection position of the oil groove sealing cover and the electric generator rotating shaft; an air inlet and a gas suction opening are formed in the oil groove sealing cover; a suction pipe is arranged on the gas suction opening in a matched manner; and the gas suction opening is connected with an oil mist suction and exhaust device through the suction pipe. The suction pipe is provided with an oil tank, and the sectional area of the oil tank is greater than that of the suction pipe. According to the structure, a gap existing between the electric generator rotating shaft and the sealing cover is effectively blocked, so that the oil mist is prevented from overflowing from the gap; and the oil tank has the condensation and deposition effects, so that oil-containing gas in the pipe is condensed and deposited in the oil tank, oil is separated from the gas automatically and deposited in the oil tank, the amount of oil entering the oil mist suction and exhaust device is reduced, and the handling burden of the oil mist suction and exhaust device is reduced.