a method and a device for detecting object properties using electro - optically modulated surface plasmon resonance based on phase detection is disclosed . in the case of a surface plasmon resonance sensing device according to the present invention , the voltage is applied on the sensing device made of an electro - optic material to modulate the surface plasmon resonance condition by varying the wavevector of the incident lightwave . the relation between the phase of output optical wave and the applied voltage is measured , and the solution concentration or the material property is obtained by using the slope of a regression straight line of this relations . the invention can be used in the experimental arrangements of the attenuated - total - reflection structure and the optical waveguide structure , and has advantages of high sensitivity , high stability , small bulk , low equipment cost , etc .