Abstract: “Three nitrogen”pollution including ammonia nitrogen, nitrate nitrogen and nitrite nitrogen, which has become a common form of groundwater pollution. Study on the migration and transformation mechanism of “three nitrogen”is important to control shallow groundwater pollution. Sandy loam of surrounding areas in Haikou Nandu River was taken as the research medium, migration and transformation of“three nitrogen”were studied under 100 mg/L nitrogen solution leaching under the pH value of 6.5, 5.5 and 4.5 by soil column leaching experiment. The results showed that the concentration of NH4 +-N, NO2--N and NO3--N decreased from No.1 to No.3 sampling point under pH 6.5 and 5.5, which was mainly due to the adsorption of soil and nitrification and denitrification. The removal efficiencies of NH4+-N, NO2--N and NO3--N were 57.2%, 65.3% and 91.6%, respectively, under pH 6.5, but they were 46.3%, 61.2% and 60.4%, respectively, under pH 5.5. pH 6.5 was in the optimal pH range of adsorption, nitrification and denitrification, and it had the highest removal efficiency of“three nitrogen”. The concentration of NO2--N increased from 141.3 g/L to 147 g/L at pH 4.5, and the concentration of NO3--N increased from 11.3 mg/L to 34.56 mg/L, it indicated that nitrification and denitrification were inhibited by acid environment, and the absorption efficiency was week, which might lead to the accumulation of NO2--N and NO3--N in soil. The soil in Hainan area was acidic, the concentration of“three nitrogen”in groundwater should be monitored timely and corresponding measures should be taken to control the pollution.