For hazardous air pollutants(HAP) such as NO, NO₂ and SO₂ decomposition efficiency, power consumption, and applied voltage were investigated by SPCP(Surface induced discharge Plasma Chemical Processing) reactor to obtain optimum process variables and maximum decomposition efficiencies. Decomposition efficiency of HAP with various electric frequencies(5∼50 ㎑), flow rates(100∼1,000 mL/min), initial concentrations(100∼1,000 ppm) and additive(CH₄) were measured and the products were analyzed with FT-IR. Experimental results showed that for the frequency of 10 ㎑, the highest decomposition efficiency of 94.3 % for NO, 84.7 % for NO₂ and 99 % far SO₂ were observed at the power consumptions of 19.8, 20 and 19W, respectively, and that decomposition efficiency decreased with increasing frequency above 20 ㎑. And decomposition efficiency per unit power were 5.21 %/W for S02, 4.76 %/W for NO and 4.24 %/W for NO₂ and the highest decomposition efficiency was observed with SO₂. Decomposition efficiency was increased with increasing residence times and with decreasing initial concentration of pollutants. When the additive of CH₄ was used, decomposition efficiency was increased with increasing CH₄ content, and NO, NO₂ and SO₂ were almost completely decomposed with the efficiency of 99 %, 98 % and 99 %, respectively and therefore CH₄ was a good additive material. The optimum power for the maximum decomposition efficiency were 7.5 W for SO₂, 9.5 W for NO and 15.5 W for NO₂, respectively. Optimum power with the maximum decomposition efficiency were 9.5 W at 1,000 ppm of NO, 7∼8 W at 100∼500 ppm of NO and 15.5 W at all concentration range of NO₂ and 11.5 W at 1,000 ppm, 4.9 W at 500 ppm, 3.7 W at 100∼300 ppm of SO₂ and power efficiency was best in these case.