A method of recycling waste plastic foam materials firstly is to smash a waste material including polyurethane foam into fine particles so as to obtain a first starting material. The first starting material is then crisped and followingly milled into powder so as to obtain a second starting material. The second starting material is then placed into a mixer to mix with a first foaming reaction solution including polyol, catalyst and additives injected into the mixer so as to form a semi-treated foaming material. And then, the semi-treated foaming material is mixed with a second foaming reaction solution including diisocyanate injected into the mixer so as to obtain a completed-treated foaming material. Lastly, the completed-treated foaming material is poured into a mold and then water vapor is uniformly introduced into the mold so as to induce the completed-treated foaming material to proceed foaming reaction.