The 610 nm AlGaInP LEDs was prepared by MOCVD on the n+-GaAs(n=1×1018 cm-3), the X-ray double crystal diffraction and spatial PL spectrum map was used to analyze the AlGalnP epitaxial layers. Through the degenerate experiment of diffent thickness AlGalnP LED in the same condition, we found that the degenerate of LED luminance diminishes with the decrease of the GaAs substrate thickness. With the calculated result, we can get that the main reason that the better reliability of LED luminance with the decrease of the GaAs substrate thickness is the decreased heat out form the thin substract, and the decrease of the GaAs substrate thickness can also help to improve the reliability of AlGalnP LED device.