We carried out basic study on the major odor substances from livestock waste treatment plant to design high efficiency offensive odor treatment facility. We choose Y and G-treatment plants and measured each samples from pre-treatment facility, water treatment facility, sludge treatment facility and offensive odor treatment facility. The odor was mainly produced from pre-treatment facility from above measurements. The concentration of hydrogen sulfide was very high as 1,200 ppm from impurity treatment facility. The concentration of hydrogen sulfide was detected as 100 ppm in waste water treatment facility(aeration facility and head) and 160∼252 ppm in sludgy treatment facility (retaining facility and scum tank). The offensive odor treatment facility was composed of washing tower using NaOCl as washing material and bio-filter. Efficiency of the offensive odor treatment facility on the hydrogen sulfide was 5∼33% and the efficiency on the ammonia was low except Y-treatment facility’s vortex mixer washing tower which is 98%. Reduction efficiency of hydrogen sulfide was increased from 14.7% to 96.3% by changing washing material, NaOH, at Y-treatment facility’s vortex mixer washing tower.