Abstract: The relationship between the shrinking and swelling of plant stems and crop moisture content is the key problem. Based on large numbers of literature from 1950s to 2004, this paper analyzed and evaluated aclvances on diagnosis method of crop moisture content using changes in stem diameters of crops, and summarized the main research progress in diagnosis of crop moisture content condition from changes in stem diameters of plants. The problems of studies in this field were also pointed out. Furthermore, the trend of research and development in the future was prospected.