Abstract: Study of the evaporation is one of crucial technology in AVLIS (atomic vapor laser isotopic separation). The research work on physical parameters of atomic vapor in separation region such as the 2 D distributions of velocity, density and temperature provides some important scientific data for designing separator in AVLIS engineering. In the paper, the distribution of density, velocity and temperature is presented and some related interpretations for them are also given on the basis of BGK equation, when many absorbing boards are considered.