Abstract: The working principle of the optic-fiber Surface Plasmon Resonance (SPR) sensor is based on the resonance of the surface plasmon. SPR sensor has been applied to measure the refractive index of surrounding material. By establishing the correspondence relationship between SPR signal and the surrounding material, the inside information influenced by refractive index can be studied. The basic concept, detection system and method used to measure the content of chlorophyll by optic-fiber Surface Plasmon Resonance sensor are introduced. The relationship between the resonant wavelength and the content of chlorophyll found through experiments can be utilized to test the content of chlorophyll fast and accurately with the help of the SPW sensor.