Raman spectroscopy (RS) is a unique analytical technique that probes molecular vibrations, and provides specific information about the structure and conformation of biomolecular constituents in biological tissues. Its capabilities for fast, accurate, and noninvasive/minimally invasive analysis have facilitated clinical applications in early cancer detection and pathophysiological investigations. Recent technology advancement in lasers, optical fiber probes and photoelectric devices has resulted in new rapid Raman spectroscopy systems with significantly better performance for real-time clinical measurements. Thereby, the scope and depth of its clinical usages have been expanded and deepened with the manifestation of its scientific connotation and diagnostic value. This short review provided an introduction to the theory and technology behind the development of integrated real-time Raman system for in vivo cancer detection. The perspective of its clinical utility, exemplified with skin and lung cancer detection, was presented with the intention of providing a useful reference for relevant basic research and technical innovation.