Dental plaque is one of the main etiologic factors that lead to dental caries and periodontal disease, and the amount of plaque on teeth could be served as reference for the teeth health condition to some extent. Therefore, the detection of dental plaque plays a very important role for maintaining the oral health. However, identification of dental plaque is difficult for both patient and dentist because the tooth and dental plaque often look similar, especially when plaque is present in scanty amounts. Excited by the light source with the wavelength of 405 nm, the auto-fluorescence effect will appear in both dental plaque and dental tissue, but the auto-fluorescence spectrum of dental tissue mainly locates at the wavelength range of blue and green light, while the auto-fluorescence spectrum of dental plaque mainly locates at the wavelength range of red light, and the spectrum intensity caused by the different leveled dental plaque are also diverse. Based on the differences between auto-fluorescence spectra of dental plaque and dental tissues, a potable auto-fluorescence color imaging dental plaque detection system was developed. In the detection system, five surface-mounted LEDs whose central wavelength are all 405 nm are assembled as the excitation source, besides, a long pass optical filter with central wavelength of 520 nm is configured to improve the signal to noise ratio (SNR), and the excited auto-fluorescence was collected and imaged through the imaging lens to the array sensor of a color CCD with a resolution of 640×480. Finally, the amount of dental plaque is analyzed by processing the captured fluorescence images. An experiment was designed to confirm the reliability of the detection system. The anterior teeth auto-fluore