Two heteropoly zinc salts of Zn1.2H1.8PW12O40 and Zn1.1H1.9PMo12O40 are prepared by template impregnation. They are used as catalyst to oxidative degradation of 4,4′-dibromobiphenyl (4,4′-DBB) in subcritical water. Zn1.2H1.8PW12O40 pays better role on accelerating degradation rate and shows enough stability. Thus oxidative degradation and the kinetics of 4,4′-DBB in subcritical water are investigated using Zn1.2H1.8PW12O40 as catalyst. The optimal experiment conditions are obtained as follows: m(H2O2)∶m(4,4′-DBB)= 200∶1, temperature of 320 ℃, pressure of 11.9 MPa, and reaction time of 15 min. Under the optimal condition, chemical oxygen demand （COD） of water sample after reaction can be down to 55.9 mg/L, which meets the Chinese National Standard GB 8978—1996. The order of catalytic oxidation degradation kinetic of 4,4′-DBB in subcritical water is 1.70, and the apparent activation energy is 44.04 kJ/mol.
