The theory of mode capability matching in fiber probe of evanescent wave fiber-optic biosensor is analysed and a system of evanescent wave fiber-optic biosensor with new configuration is constructed.The system sensitivity affected by the degree of mode matching in fiber probe is studied.Experiments are carried in two cases

one is that the probes are put in airs and the other is that the probes are put in water.Five groups of probe with different core radius in two cases are tested.The experiment results show that the curve which is ralationship between the system’s detected fluorescent signal-to-noise ratio and the radius of the probe core conforms to the theory curve of the mode matching on the whole.