Abstract: To provide reference for data correction of the cryogenic wind tunnel, the vechicle's aerodynamic character is researched with numerical method. In the research, the real gas effect on vehicle is studied through the comparison between real low temperature gas and perfect gas, and the ratio of real gas effect to Reynolds number effect is also studied. Employing Aungier-Redlich-Kwongz equation, a new RANS code is developed, to research the real gas effect of nitrogen in cryogenic and high-pressure condition. Comparing with NIST data, Aungier-Redlich-Kwongz equation maintains the deviation of specific heat below 0.3% under 5 times atm pressure. Also, standard model test indicates that the current code is comparable to international softwares. Researches are taking on the real gas effect of nitrogen in cryogenic wind tunnel with the current code. The typical transport aircraft of DLRF6 is selected as the calculation model, and its surrounding flowfields are obtained in different conditions, such as different inflow speeds, temperatures and pressures. The calculation results show that, in the low temperature and enhanced pressure condition, the variation from the real gas effect is rather low, and the relative deviations of lift, drag and moment are all below 0.3%, which are neglectable to the effect of Renolds number. Thus, the medium of nitrogen in cryogenic wind tunnel can be assumed to be perfect gas in the experiment analysis.