A novel grating device composed of a polymer dispersed liquid crystal (PDLC) film and a periodic striped electrode structure has been demonstrated. Due to PDLC electrooptical properties, this grating can cause scattering or diffraction of an incident light dependent upon the applied voltage. i.e. it is adjustable by electric field. Results show that when the applied voltage is higher than its threshold voltage, both diffraction light intensities and visible orders can be controlled electrically. Moreover, the linear polarization state of the incident light can be changed into an elliptical polarization state.