Abstract: The sand particle velocity and concentration ofsolid-gas two phase flow are studied inthe environmental test equipment with gravity applied on top. Using the wind tunnel of CAREERI ofCAS and applying laser digital particle imaging technology, theparticle velocity and space distribution in different sections of thesand orifice along the wind horizontal direction is determined.In this paper, it is shown that the particle velocity can approach thewind velocity and theparticle can just diffuse to the whole space only in the section that is about threemeters horizontally from the sand orifice. It providesa basis to develop the large-scale sand and dust experimental testequipment.