To judge the range and level of water pollution impact in provincial buffer zone and ensure the management of polluting red line for water function zone in Pearl River basin to be fair and justice, we drew up the water pollution impact evaluating method for provincial buffer zone in Pearl river basin and testified it with real examples, based on the character of water resources in provincial buffer zone of Pearl River basin and the water function zone supervision and monitoring work. The result shows that our evaluating method is scientific and its results are reasonable. The method is practical for water quality evaluation of water function zone in Pearl River basin, can provide strong support for the assessment under the strictest water resource management standard for Pearl River basin.