Taking the farmland with summer corn and winter wheat rotation in Dagu River downstream of Qingdao as the study object, the dynamic characteristics of nitrate nitrogen in soil at different depths and groundwater in the rotation period were revealed through field experiment and lab analysis. The impacts of fertilization and irrigation on nitrate in soil and groundwater were explored and the nitrate pollution process in soil and groundwater based on the theory of soil water dynamics and solute transport was numerically simulated. Nitrate content exceeded 10 mg/kg at the depth of 130 – 160 cm at the end of the season, when the nitrogen rates reached N 380 kg/hm² in wheat season and 290 kg/hm² in corn season. A monthly cumulative model of nitrate in groundwater was established. Results showed that monthly cumulant of groundwater nitrate was higher in June and August with the values of 7.20 mg/L and 7.67 mg/L respectively.