The invention discloses a component for absorbing sustainable one-way emission moisture in a small and micro space, a manufacture method thereof, and a car lamp rear cover. The component comprises that the end surface of one side of a barrel is connected with an expanded polytetrafluoroethylene coating membrane with the lyophobic and oleophobic ability which persistently discharge moisture in oneway, the end surface of the other side is connected with a thin membrane with moisture permeation ducts, and the barrel is full of reversible moisture absorption particle substances. The preparation method comprises the following steps: connecting and welding the die cutting product of the expanded polytetrafluoroethylene coating membrane with the end surface of one side of the barrel, filling thebarrel with the reversible moisture adsorption particle substances, and final, welding the die cutting product of the thin membrane to the end surface of the other side of the barrel. The car lamp rear cover comprises the components, wherein the components are assembled in a rear cover shell with a plurality of through holes. Through the above way, the ability for discharging moisture in the carlamp shell to the external environment of small and micro spaces, such as car lamps and the like can be improved, and therefore, the moisture in the small and micro space such as the car lamp shell can be lowered to the minimum degree.