Abstract: The tandem organic light-emitting devices have problem that chromaticity coordinate change with voltage and brightness, which seriously affects display and lighting effects. This paper mainly studies the influence of anode thickness variation on chromaticity coordinate variations under different brightness, and characterizes it using MacAdam ellipses. The results show that increasing the anode thickness is beneficial to improving stability of the chromaticity coordinate, and achieving a brightness range from 1 cd/m² to 1000 cd/m², with the chromaticity coordinate variations of (0.052， 0.007). This research provides a direction for further optimizing the tandem devices to improve chromaticity coordinate stability.