This study was conducted for the purpose of assessing the pollutant removal possibilities of sedimentation pool formed by deep dredging of a reservoir inlet. Water quality data were collected in the Masan reservoir, whose inlet has been dredged deep like sedimentation pool. The average concentration of chemical oxygen demand(COD), toatal nitrogen(T-N) and total phosphorous(T-P) in the deep dredged area were 8.3~28.4mg/ ℓ (COD), 2.0~6.0mg/ ℓ (T-N), 0.17~1.34mg/ ℓ (T-P), which were 3.3% (COD), 30.6%(T-N) and 46.4%(T-P) higher than those of middle part of the reservoir. From these results, it was considered the deep dredged area in the inlet of reservoir might play a key role to improve reservoir water quality.