Abstract: Using growth speed as well as COD_Mn, UV₂₅₄ and Color₄₁₀ degradation abilities in humic acid (HA) slightly polluted waster as a standard for screening HA-degrading bacteria. A strain of bacterium was screened out and marked as strain F5 among 20 strains of bacteria isolated from a biological activated carbon (BAC) reactor in a water purification plant. The homology of strain F5 with Acidovorax sp. MN33.2 was 99%. In the ranges of initial HA concentration 5-20 mg/L, pH 3-8, and water temperature 20-35 ℃ at reaction time 24 hours, COD_Mn removal rate by using the strain F5 increased with the increase of initial HA concentration or temperature, or with the decrease of pH. Under the initial HA concentration of 20 mg/L, pH of 7.0, water temperature of 20 ℃ and reaction time of 48 hours, COD_Mn removal rate by using strain F5 reached 49.1%.