In order to solve the problem of mass concentration of pesticide fog after application in airtight space, an improved container collecting the air samples was used at different locations in the level of 1.5m from ground, and curved surface of mass concentration of pesticide fog was established based on cubic spline interpolation. It was showed that the pesticide mass concentration attains maximum at 10～12m in the front of the nozzle, and the effective regional of cold aerosol sprayer is 42m, from 10m in the back of the nozzle to 32m in the front of the nozzle, in length; and the pesticide mass concentration was lower in the middle of airtight space than the sides of it, in width. 