A nanofiltration (NF) membrane of high performance was prepared through interfacial polymerization using two kinds of acyl chloride monomers. A tetra-functional 2,2',4,4'-biphenyl tetraacyl chloride(BTEC) was partially replaced by a novel acyl chloride with a -PO(Cl)(2) group, namely 5-(dichlorophosphoryl)isophthaloyl dichloride (5-DCPO-IPDC). When the ratio of the concentration of 5-DCPO-IPDC to the concentrations of 5-DCPO-IPDC and BTEC was 60%, an excellent NF membrane was acquired, of which the salt rejection of Na2SO4 and NaCl were 99.0% and 48.8%, and the pure water flux was 86 L/m(2) h tested by 2000 ppm feed solution at 25 degrees C and 0.48 MPa. Compared with the commercial NF270, the water flux of our membrane was 1.45 times to that of NF270 under 99.0% rejection of Na2SO4. The testing results of XPS and zeta potentials illustrated amounts of phosphoric acid groups existed on membrane surface because of the hydrolysis of -PO(Cl)(2) which increased the negative charges in active layer. The molecular weight cut off (MWCO) was tested to characterize the effective pores sizes of membrane and the value was about 700 Da, demonstrating we obtained a "loose" active layer. Finally, through adjusting the balance of charges and pores sizes in membranes, a NF membrane of high desalination performance was successfully prepared.