Abstract: When a microporous hydrophobic membrane separates two aqueous solutions at dif-ferent temperature, a selective mass transfer across the membrane can be obtained. Mem-brane distillation may be used to solve some waste water problems, chemical separation and recovery, and concentration of aqeuous solution of substance which is sensitive to high temperature, with simple equipment. It is particularly attractive and promising. In this paper, the mechanism of the membrane distillation is described, and some information about membrane distillation of aqueous solution and other applications are in-troduced.