Total 109 precipitation samples were collected in north suburb of Nanjing from March to June 2011.In order to investigate the chemistry characteristics of precipitation,the concentration of water-soluble ions were analyzed and the air mass sources of precipitation were also discussed using the back trajectory model.Results show that the precipitation is mainly controlled by southern and northern air masses,and the concentrations of major ions from precipitation of northern air masses are higher than those from southern.The sea salt tracer method and the correlation analysis indicate that NO₃^- and SO₄^2- are mainly from coal burning,industrial emissions and vehicle exhaust emissions.Ca²⁺ and Cl^- mainly derive from crustal and marine sources,respectively.K⁺ and Mg²⁺ are both from marine and terrestrial sources,while the terrestrial contribution of Mg²⁺ is dominant,and the impact of marine on K⁺ is lower than on Mg²⁺.Due to the scavenging process,the concentrations of different ions and the enrichment factors of main ions in the early period of precipitation are higher than those in the whole period of precipitation,which are attributed to the main contribution of local pollution sources.