molecular weight of the spfr is preferably 300 to 3000 more preferably 400 to 1500 from the viewpoint of water solubility effect and handling an aqueous solution of the spfr thus prepared is neutral or acidic by sulfonation of the phenol and therefore gives no discoloration of the paper product and exerts stable yield improving effect and freeness improving effect in the method of the present invention said spfr is used in combination with peo as the yield and freeness improving agent and the weight ratio of spfr to peo is preferably 0 1 to 5 1 more preferably 0 5 to 2 1 the concentrations of spfr and peo added are preferably 0 005 to 0 05 and 0 001 to 0 03 respectively based on the paper stuff solid in such concentrations the yield and the freeness can be improved in the paper making and waste water treating process examples wherein the spfrs of the invention are used as the yield improving agent in paper making are shown as follows to illustrate the present invention however the present invention is not resticted to these examples equipment dynamic drainage jar abbreviated to ddj made by paper chemisty laboratory inc method 500 ml of paper stuff was fed.