Abstract: The current situation of sludge composting as fertilizer and its environmental impacts are reviewed. The impacts include accumulation of heavy metals, influence of agglutinant and harmful organic pollutant, secondary pollution with excess nixrogen and phosporus, odor, pathogenic bacteria and so on. The related counter-measures for these impacts are also suggested. Reinforcing environmental management, limiting the quantity of sludge and sludge composting as fertilizer are proper ways for solving sludge problem.