An image analysis system for determining cancerous cells includes an acquisition module, an image capturing module and a multi-spectral image reproduction module. A method for determining cancerous cells includes a spectral database establishing procedure of cancerous cells and a cell determining procedure of multi-spectral image reproduction. The spectral database establishing procedure includes a penetration spectrum analysis step and a database establishing step. The cell determining procedure is based on the cancerous spectrum database and includes an image capturing step, a cell location contouring step, a penetration spectrum analyzing step, a classifying step, a color gaining step, an image reproduction step and a cell determining step.