A theoretical analysis of the attenuation coefficient and its modification of 10.6 m laser beam passing through the dust-storm has been made with an approximate method. A series of results of digital calculation for the samples of dust-storm in desert area were obtained by using electronic computer. The result shows that under the ordinary dust-storm weather condition, the attenuation coefficient is mainly within the range of 3~5db/km, and the maximum is about 7db/km.