Abstract: Ji-7 wellblock in Changji oilfield is a deep and large heavy oil reservoir. Aiming at the situation of poor liquid supply, fast production decline and discontinuous production coming from part of the oil wells in southern, the research and application of nitrogen-assisted chemical viscosity reduction technology are carried out. Combined with the reservoir property of Ji-7 wellblock, the adaptability of viscosity reducer was evaluated. The experiment results show that the viscosity agent has good effect of viscosity reduction (quality percentage 1.5%, viscosity reduction rate from 75% to 85%) in the condition of reservoir temperature and salinity in Ji-7 wellblock. The field tests show that the application of this technology can solve the problems mentioned above. This technology has applied for eight wells, and increased total 1011.2 tons of oil.Nitrogen assisted technology can play an obvious role in assisting drainage and controlling the water cut rising of oil wells.