CD90 is a kind of glycoprotein on the surface of cell membrane, which could express in a variety of normal tissue cells. It is mainly responsible for the regulation of interactions between cells or between the cell and matrix. Recently, some researchers isolated CD90 positive cells from different tumor tissues, such as esophageal cancer, lung cancer, breast cancer, liver cancer, etc., and confirmed that these cells could represent the main characteristic of cancer stem cells. Some studies also confirmed that CD90 was involved in the regulation mechanism of tumor microenvironment, and its expression was associated with prognosis of tumor. The research of CD90 in different tumors including the tumor of digestive system, nervous system, urinary system, female reproductive system and other tumors were introduced in this text. In a word, CD90 is expected to become a molecular marker of tumor diagnosis or differential diagnosis and a new target for malignant tumor therapy.