Environmental scanning electron microscope(ESEM)plays an important role in research and casework in forensic science．It not only has the functions of traditional scanning electron microscope，but also can adjust the humidity and the air pressure of the sample chamber．With ESEM，we can obtain the secondary electronic imaging in natural condition．Therefore， it can be used tO observe the surface ultrastructure of non-conducting and non-heat—conducting samples directly．These characteristics decide that the ESEM will have a broad application prospect in the field of forensic science．