The cracks of fissured soils are important factors that affect the soil engineering properties. To study the process of crack evolution under changing environmental conditions
an experimental device that can precisely control the humidity is designed; and the process of crack formation
propagation and extending reappears by using this device. The experimental results have been theoretically analyzed; and the disciplinarians of crack emergence
propagation and extending in the experiment have been educed. The research results could do help to the comprehension of the physical changing process of soil cracks and provide considerations to deal with the engineering problems.