Abstract: Being main material of coating agent, the emulsion of PTFE was used to coat the surface of P84/PTFE compound filtering media by means of foam coating. The effect of coating on the structrue and properties of compound filtration medium was studied. The results indicated shat the compound filter after coating had better properties of heat shrinkage, acid resistance and alkali resistance, because of a dense porous coating of PTFE formed on the filter surface. Also filtration performance was improved obviously.