Abstract: Henan oilfield heavy oil thermal recovery steam soaking began in1987 and It has been carried out for 24 years. In order to improve the development effect, nitrogen slug injection thermal treatment field experiment is carried out in 2011. Periodic oil steam ratio and oil production increased relevantly. In the paper, the stage effect of nitrogen slug injection is recorded, the factors influencing different viscosity heavy oil reservoir is analyzed, which made it clear for well selection conditions and scope of application for the heat treatment technology of nitrogen slug and provide a basis for the following work.