Abstract: There is no possibilities to realize the full similarity of the experiment of indoor model of blownsand phenomena. It is impossible to make full similarity between the indoor experiment on phenomena of blownsand and that in nature, a) it is difficult to enable the model to be geometrically similar to material object, for instance, when sand grains in air current were reduced in accordance with the reduced scale of the model, the physical nature accordance with the reduced scale of the model, the physical nature of sand grains in air current will be fully changed; b) it is complicated to meet the needs of similar criterion and technologically it is impossible to realize. If two most important criterion of Re coefficient and Fr coefficient were met, the kinematic medium ueed to be changed or the acceleration of gravity on earth should be changed. This is very difficult to realize on the viewpoint of technigue and therefore only the approximate method of similarity can be adopted and only one much more important criterion of similarity could be considered.