The invention discloses an oil retaining and looseness preventing device for a bearing. The device comprises a fan frame, a fan frame middle tube, an oil-containing bearing, a rotor, a stator and fan blades, wherein the rotor comprises an axial core; the oil-containing bearing sleeves the axial core; the fan frame middle tube sleeves the oil-containing bearing, and is arranged at the bottom of the fan frame; the fan frame middle tube is located between the stator and the axial core; the fan blades are fixed on the rotor; an oil retaining structure is arranged between the upper end of the fan frame middle tube and the oil-containing bearing; the oil retaining structure is a circular sealing ring; the circular sealing ring is fixed at the tube orifice of the upper end of the fan frame middle tube; and an oil gathering region is formed among the circular sealing ring, the fan frame middle tube, the oil-containing bearing, the axial core, and the fan blades HUB. According to the oil retaining and looseness preventing device disclosed by the invention, the sealing ring in the oil retaining structure is independently used, so that the wire winding operation and the assembly of a motor are not influenced, and the bearing and the stator are relatively easy to assemble; and the sealing ring which is independently used and the middle tube are in tight fit, so that leakproofness is improved, lubricating oil is effectively prevented from leaking, and the bearing is fixed.