Under the operation of multifunctional device for water lifting and aeration(MDWLA), in situ simulation experiment is made by use of the oligotrophic biofilm process for pretreatment of micro-polluted raw water in order to investigate the removal effects of nitrogen and organic matter. The experimental results show that the combined technique of water-lifting aeration and oligotrophic biofilm process is feasible, and the removal rate of ammonia, nitrate, total nitrogen and TOC in steady running period range from 82%~100%, 62%~79%, 71%~80% and 73%~80%, respectively, under the condition of temperature 10~23 ℃, dissolved oxygen 4.0~6.0 mg/L, NH +4-N 0.230 mg/L, NO -2-N 0.010 mg/L, NO -3-N 1.125 mg/L, TN 2.010 mg/L, CODMn 3.140 mg/L and BOD5 1.540 mg/L for source water, also the nitrite is poorly detected and the ratio of BOD5 to CODMn is in the range of 0.05 to 0.20. Obviously, the nitrogen removal effects can meet the requirements of class Ⅲ of surface water quality according to GB3838—2002 and the biological stability can be improved under stable operation condition of the combined process. Lastly, the changes of oligotrophic denitrifying bacteria number and biological phase, and water purifying mechanism of oligotrophic biofilm system are also discussed.