1. A method for processing a block to be processed of a urine sediment image, comprising: approximating the color of a pixel in a block to be processed to one of the k c colors in a code book, wherein the code book is a set of the k c colors generated in a set of urine sample blocks, the k c colors are formed by clustering the colors extracted from the urine sample blocks in the set, and k c is a positive integer; obtaining a distribution histogram of the number of pixels the color approximation results of which fall on each color of the k c colors in the block to be processed; using an occurrence frequency correction factor to correct the number of pixels the color approximation results of which fall on each color in the distribution histogram; standardizing the corrected number of pixels the color approximation results of which fall on each color in the distribution histogram; and by way of taking the standardized distribution histogram as a feature in a feature set of block processing, processing the block to be processed.