The invention relates to a method for determining the use amount of spot color ink. The existing method for determining the ink use level mainly depends on manual work, thus having poor accuracy and being hard to master. The method comprises: reading in the digital file of a printing movable piece which requires for blending spot color ink by a computer; calculating the image-text area coverage rate of a spot color version; according to the required printing ink layer thickness requirements and printing amount, determining the total use amount of the ink on a printing stock; according to the structural characteristics of a printer ink transmission system, calculating the ink amount required for storing by the printer ink transmission system; calculating the minimum storage ink amount of an ink fountain and ink loss in the printing process; and integrating the ink consumption amount of the aspects to obtain the total ink use amount required to print the spot color. The invention can improve the accuracy for blending the spot color ink amount, reduces material waste because of too much ink and reduces time waste because of too little ink.