During the cloth printing, the calculation about quantity of dyestuff is considered as adifficulty to the printing and dyeing company for a long time, In the paper, a method of quantitycalculation is proposed, At first, using the digital vidicon, the picture of colorful cloth is picked upand storage in computer. With the computer image processing technology, the image smoothing,yawp wiping off, image threshold choosing, image dividing and so on can be made thoroughly. Onthis basis every homochromatic cloth image and its number of pixels and then the realhomochromatic cloth area can be obtained. Several factors which affect the quantity of dyestuffare taken into account. With the whole procedure taken, the dyestuff quantity can be calculatedexactly.