An AMOLED display device based ELVDD power supply method and power supply apparatus, and a display device are provided. The method includes: acquiring a data signal of each pixel in one frame of image; comparing a gray scale value corresponding to the data signal of each pixel with at least two threshold gray scale values; taking a minimum threshold gray scale value in the threshold gray scale values greater than the gray scale value corresponding to the data signal of each pixel as a target gray scale value of the pixel; and taking a maximum target gray scale value in the target gray scale values of all pixels as a maximum gray scale value of the one frame of image, and driving the one frame of image by an ELVDD corresponding to the maximum gray scale value.