Abstract: The property of expansion and drying shrinkage of small concrete hollow blocks is one of the main causes that results in cracks of a block building; and people have attached importance to their harm. Tests were conducted with walls of the same dimension in a room designed by ourselves to ensure invariable relative humidity. Through the tests, the influence of relative humidity, time, duration surfacing materials on deformation of block walls was investigated. Also, the shrinkage ratio of block walls was achieved under 65% relative humidity and 45% relative humidity, which may be a reference for the design of such walls.