This paper proposed an optical compensation scheme for a-IGZO AMOLED with a high PPI pixel design solution. The PIN sensor is fabricated on the backplane and covers 8 sub-pixels. The scheme is applied to a 5 inches AMOLED display. The results shows that the characteristics of a-IGZO TFT still satisfy the needs for display. And the uniformity of the panel is improved a lot for all gray level.