Abstract: A guide-mode resonance based electro-optic modulator, which consists of a coupling prism with 4 layers of film coated, was developed. These 4 layers are metal layer, poled polymer, buffer polymer, bottom electrode. The polymer waveguide electro-optic modulator capable of attenuating total reflection was tested in the transmission of the video. A new method was proposed to stabilize mode angle with the static bias voltage. The effect of the laser noise on the analog signal modulation during the video modulation is eliminated by monitoring of incident laser beam. The operation stability was improved. The experiment results show that the electro-optic modulator has fine linearity and high sensitivity.