Abstract: Extracting methods of soil NO3-N、NH4-N by KCl solution and determining that by continuous flow analyzer were respectively used. There were many factors to influence results of soil NO3-N、NH4-N, such as soil pretreatment, concentration of KCl extracting solution and ratio of solution to soil and so on . In the paper , effects of these factors on content of soil NO3-N、NH4-N in greenhouse soil were studied, The results showed that : concentration of soil NO3-N、NH4-N in greenhouse had significant changes during air-drying and heat-drying, and contents of NO3-N、NH4-N in fresh soils was lower than air-dried soils and heat-dried soils. When 2M KCl extracting solution was used and the ratio of solution to soil is 5:1, determined results of soil NO3-N、NH4-N in greenhouse were more accurate. but fit extractant concentration and ratio of solution to soil must be selected according to the goal of the research .