A 90° mixed-mode twisted nematic liquid-crystal-on-silicon (90°-MTN LCoS) with protrusion located between the adjacent pixels is proposed to reduce the effect of fringing field.The influence of the protrusion with different widths from 0.5 μm to 0.9 μm and different heights from 0.3 μm to 0.7 μm is investigated.The results demonstrate that the invalid pixel region width can be reduced by 31.5％ via using the protrusion with the suitable width and height compared with no protrusion case,which provides a higher display quality,such as the higher reflectance and contrast ratio.