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PURPOSE: A plasma catalytic system is provided to efficiently remove NOx from exhaust gas discharged from a diesel engine by using a plasma reactor and a catalytic reactor. CONSTITUTION: A plasma catalytic system is comprised of a plasma reactor(11) supplied with DC pulse power and a catalytic reactor(12) filled with Ag and Al2O3. Exhaust gas generated from a diesel engine is treated by sequentially passing through the plasma reactor and the catalytic reactor. The plasma reactor consists of an anode and a cathode and supplies energy of 10-100J/L per unit flux of exhaust gas. The catalytic reactor is filled with a catalyst prepared by impregnating AgNO3 aqueous solution in gamma-Al2O3. The plasma reactor is operated in a normal pressure while the catalytic reactor is operated at 200-450deg.C of temperature. In the plasma reactor, NO in the exhaust gas is converted to NO2. In the catalytic reactor, NO2 is reduced to N2. Therefore, NOx in the exhaust gas is reduced.