Raman spectroscopy is a nondestructive photon spectrum detection technology that can directly detect the changes in cell molecular composition and structure, providing rapid and precise identification for cancerous cells. Because cancer is the leading cause of mortality in humans, early tumor detection has become a focus of medical research in recent years. This study introduced the concepts of various Raman detection techniques, and their diagnostic applications on clinic samples including tumor tissue, tumor pathological sections, patient serum, and cancerous single cells. It also presented the Raman spectroscopy technology's recent research advances concerning breast cancer, digestive system cancer, skin cancer, and glioma. Cancerous cells differ from normal cells in terms of the structure and quantity of biomacromolecules. Raman spectroscopy can quickly and precisely detect these differences, making its ideal for early cancer diagnosis.