As an important uncertainty factor in multidisciplinary optimization design of aerocraft, the statistical characteristics of aloft wind should be acquired accurately. The probability distribution of conditional aloft wind speed is unique, in order to facilitate the use of probability model of aloft wind for uncertainty design and reduce the amount of calculation, an analysis method of difference between probability distribution of conditional aloft wind speed and normal distribution was proposed, and the applicable condition for simplifying the distribution of probability distribution of conditional aloft wind speed to normal distribution was given. Numerical simulation results show that within latitude range of 24.3°N～42.2°N, the difference between condition aloft wind speed probability density and normal distribution probability density in different regions is trumpet-shaped in the range of 2～30 km above sea level, and the conditional aloft wind speed probability density is closest to that of normal distribution nearby the altitude of 15 km, which can be approximately assumed to be normally distributed. Based on the above work, suggestions were given for selecting the method of generating random samples when considering the uncertainty of the conditional aloft wind speed in the uncertainty design of aerocraft.