The detection of diseased cells in blood is an important method in cancer diagnosis and treatment. The existence of cancerous cells in the blood indicates that the body have been already canceration. Therefore, the identification and detection of the cancerous cells has the significant meaning in the medical science. Polarization is an inherent characteristic of light. The properties of different substances can be detected by their different polarization characteristics of light. In this article，we discussed the property of the cancerous cells firstly used the polarized light scattering method. Base on the different character in polarized light, we successfully distinguished the cancerous cells and erythrocyte, the viable cancerous cell and the dead cancerous cell. This method is non-invasive, non-in, high-sensitive and high-resolution compared to other ones. It provide the new ideas for cancer diagnosis and treatment.