This paper used the Inverse Distance Weighted (IDW) based on GIS spatial analyst platform to obtain the spatial distribution characteristic of NO3-N of a typical karst water source in the North China, and used Spearman's coefficient to obtain the relationship between the concentration of NO3-N in 2009 and various influencing factors of groundwater vulnerability. By combining with research data in the past, it can be known that the evolution process of NO3 -N in Dawu water source can be classified into early deterioration period, the mid -end deterioration period and the recovery stage, and the evolution process of groundwater chemicals lagged behind groundwater dynamics. It can be also concluded that the spatial distribution of NO3-N values in a year is mainly influenced by precipitation, while the spatial distribution of NO3-N values of inter-annual is easily influenced by dynamic factors of groundwater system including the exploration of groundwater resource and variable underlying surface conditions, the human activities develop in the direction of optimizing groundwater environment will promote the sustainable development of karst water resources.