Propagation of laser radiation in the atmosphere is susceptible to various degrading effects, one of them is attenuation due to cloud. Recenlty systematic propagation experiments of 4.6μm laser radiation were conducted under a broad range of micro-physical properties of laboratory clouds. An extensive data-base has been obtained, thus provided an opportunity to investigate extinction udner various cloud conditions and the relationship exists between cloud optical and its micro-physical properties. In addition, comparison between the extinction coefficients obtained from experimental measurement and Mie theoretical prediction was conducted. It was proven that both of them agreed favorably well with each other.