Abstract: Based on a computer program of atmospheric transmissivity-CIRTRAN(Chinese Infrared Radiation TRAN smissivity program),the atmospheric transmissivity of Nd:YAG laser at λ=1.06μm propagating in a slant path is calculated for several various visibility and four regions of rural,urban,ocean,and desert.Analyzing and synthesizing the calculated results,one present a direct and simple expression.In comparison with three different measurement method and LOWTRAN7 a very well accuracy of the experession is demonstrated.