[Objective] The paper aimed to evaluate the plain forestry＇ service function in Northwest China.[Method] Based on general and representative investigations with county used as the minimum unit,evaluation on service function of plain forestry ecosystem in Northwest China was carried out by measuring the quality and quantity.[Result] In 2005,the plain forestry in Northwest China plays a profound role in water and soil conversation,carbon sequestration by vegetation and soil,oxygen release by plants,sulfur dioxide absorption and and so on.[Conclusion] This paper laid foundation for research on service function of plain forest ecosystem in Northwest China.
