This study was conducted to analyze the effects of the UFCA for treating polluted in reservoir. The UFCA makes water mixing by circulation of surface and bottom water layers. Its circulation supplies the oxygen to bottom of reservoir, and in result water quality improvement of reservoir. We surveyed the changes of temperature, pH, transparency, depth, conductivity, DO, COD, BOD, T-N, T-P and Chlorophyll-a for 7 months from Feb. to Aug. in 2004. Temperature difference of surface and bottom of reservoir was very low because of water mixing by UFCA. pH was changed from 7 to 9. Transparency of water was about 80 cm through the all periods. Conductivity was 150 mS/cm in early Feb., but increased to 270 mS/cm in beginning of early March. DO was nearly not different with depth. Especially it kept 6 mg/l above in June and July. BOD was changed from 2.1 to 12.2 mg/l. This reservoir was not occurred eutrophication during our experiment, but compared reservoir was occurred algae-blooming. COD was changed from 5.4 to 14.5 mg/l. COD concentration of our experimental reservoir was higher than other one in starting periods, but in August that was reversed. SS concentration was changed from 13.5 to 23.5 mg/l in Feb., but it downed from 8.5~11.2 mg/l in July. T-N was changed from 1.3 to 4.9 mg/l. It increased up to 3 times at rainy season with compare to other components. But the compared reservoir increased to 40 times higher than experimental one at same period. T-P was changed from 0.04 to 0.17 mg/l. The ratio of T-N and T-P was changed from 20:1 to 40:1. It means that T-P was growth limiting factor for algae and aquatic plants. Chlorophyll-a was changed from 20 to 120 mg/l. Chlorophyll-a was connected with T-P, and its concentration increased with increment of T-P concentration. Our experimental reservoir was higher than compared one in concentrations of COD. T-N, T-P and others, but it was reversely lower than compared one in July that was most severe month in eutrophication. This means that the experimental reservoir was greatly remedied by UFCA. The UFCA accelerated the degradation of aquatic organic materials through effective supply of air with up-flow and circulation of water. We know that the UFCA was very effective in aspect of remediation of water quality of contaminated reservoir and lake.