A foam pump consisting of a pump body, a large piston, large piston rod, a small piston, a small piston rod, a over cap and a foaming mesh, which is featured by that said large piston rod is equipped with a one-way valve connected with an air cavity of said large piston and that said one-way valve adopts sleeve-shaped valve plate made of elastic materials mounted on the fixing base on the large piston rod with a stepped surface and that the upper part of said valve plate adopts conical sealing surface with increasing diameter for sealing together with the connecting hole on said large piston rod, said connecting hole connecting a gas-and-liquid mixing cavity in the large piston rod and said air cavity of said large piston. This utility is simple and practical with fine one-way air inlet effect and is easily assembled and used.