On the basis of observed data, spatial-temporal variation characteristics of soil moistures is studied for several kinds of typical underlying surface in humid area and desert region near oasis. The results show that soil moisture follows a β distribution in the humid area in summer,while it does Γ distribution in the desert area in the vicinity of oasis in winter.It also shows that there exits a periodic variation of soil water content ranging from ten to twenty five days in the humid area in summer.