The invention discloses a vehicle lamp rear cover with functions of dryness maintaining, temperature reducing, micro filtering and demisting in a housing. The rear cover comprises a housing and functional assemblies arranged in the housing, a plurality of fence holes are formed in the housing, air circulating channels are formed between the fence holes and the functional assemblies, the surfaces of the fence holes are covered with valve pieces, the valve pieces are fixed through a pressing cover, and an air permeable membrane patch covers the surface of the pressing cover. According to the vehicle lamp rear cover, mist forming and water drop condensing do not take place in internal electrical electronic components, vehicle lamp glass housing mirror surface and the like of the vehicle lamp,the temperature of the interior of the housing is reduced, the ageing and deforming of interior plastic materials in the housing are prevented, and the performance can be effectively and reliably achieved.