The utility model relates to a lower evacuation compressing mould for porous bricks, which comprises an upper mould carrier and a mould frame, wherein, the mould carrier is provided with a mould frame, the mould carrier is provided with a moulding cavity of which the top and the bottom are communicated with each other, and the upper mould assembly is positioned above the mould frame. The utility model is characterized in that the utility model also comprises a lower mould assembly and an evacuating assembly which are positioned in the mould carrier and below the mould frame, wherein, the lower mould assembly comprises a lower mould plate, a lower mould seat and a lower mould push plate which are connected in sequence from top to bottom, and the evacuating assembly comprises an evacuating pin, an evacuating seat and an evacuating plate which are connected in sequence from top to bottom. The lower mould plate of the lower mould assembly is positioned in the moulding cavity of the mould frame and can move up and down along the moulding cavity. The lower mould plate is provided with a through pore of which the top and the bottom are communicated with each other, and through slotted pores of which the tops and the bottoms are communicated with each other are arranged in the lower mould seat and the lower mould push plate. The evacuating pin and the evacuating seat are sheathed in the through slotted pores, the evacuating pin movably penetrates through the through pore of the lower mould plate, and the evacuating plate is positioned below the lower mould push plate. The utility model can be used for manufacturing products with smooth and beautiful appearances.