The protein skimmer mainly includes reaction chamber, collection cup, venturi injector and venturi pump. Protein fractionation process is simple but highly effective, through the ozone and air which is injected into the water to be treated, in the form of tiny bubbles, by a ozone-resistant pressure venturi injector. The organics in the water are attracted on the bubble surface(air/water interface), the bubbles rise up through a water column inside the protein skimmer to the waste collection cup and is discharged finally. Consequently, the proteins, amino acids, fatty acids, carbohydrates, enzymes, organic debris, algae, inorganic compounds, protozoa, etc. in the water are removed with the foam.