We developed the new colorimetric analysis system with the KOITO white light laser. The KOITO white light laser is a hollow cathode He-Cd laser device that simultane ously oscillates three light laser beams of three primary colors (red, green, blue) from a single laser tube. These beams are formed into a white light laser. In addition, because the oscillation wavelengths of red (635.5 nm, 636 nm), green (533.7 nm, 537.8 nm), blue (441.6 nm) color light are very near the ideal three primary colors.This system has three character. First character is non-contact type without integral sphere. Second is using pen-type probe which contain the bundle type fiber. Third is recording the rate to three colors in the standard reflex light.We examined the efficacy of this colorimetric analysis system with experimental study and clinical cases. On the other hand, we improved this system in the diagnosis of oral malignant tumor.Using this system, we could measure the color disorders in the oral cavity non-invasively, easily, immediately, exactly. Moreover we performed spectral analysis in patients with an oral squamous cell carcinoma. We found that there were bimodal peak at 650 and 690 nm at the excitation wavelength of 441.6 nm and that this result is different from the normal autofluorescenc.We consider that this coloriometric analysis system is useful to measure the color disorders in the oral cavity and has possibility to be improved in the diagnosis of oral malignant tumor.