In the optical phased array chip, the performance of the antenna unit directly determines the efficiency of the light wave energy in the waveguide to radiate outward. On this basis, the optimized design was mainly for the sector antenna. By adding a shallow etching area and a thin silicon strip to the sector antenna, the downward diffraction loss and back reflection loss of the antenna were suppressed, as well as the upward diffraction of the antenna was greatly improved. In addition, design schemes were formulated for the design requirements of improving the upward diffraction efficiency and reducing the design size. For the high diffraction efficiency scheme, the upward diffraction efficiency of the antenna reached 81.6%, the downward diffraction efficiency was reduced to 4%, and the back reflection was reduced to 1.4%. For the miniaturization scheme, the upward diffraction efficiency of the antenna was 67.2%, the downward diffraction was reduced to 5.6%, and the back reflection was reduced to 1.2%, which greatly improved the integration and emission efficiency of the optical phased array chip.