The invention discloses a blending method for mixed coal of a boiler. The method is characterized in that the coal quality is used as an optimization target, the blending method can be used for finding a scheme closest to a target coal quality from a complex single coal source; due to the fact that the components in the coal are more, the mixed coal quality obtained by blending cannot be completely the same as the target coal quality; the blending scheme is not completely the same as the target coal, but is closest to the target coal; and the proximity degree of the component in the mixed coaland the target coal can be independently adjusted by setting an expected error of a certain component. According to the scheme of taking the target coal as a blending optimization objective, the maximum output requirement of a generator set can be met in the market environment of which the coal quality is generally reduced and no stable coal sources exist, the situations that the boiler heating surface is overheated and a hearth is coked in large area are avoided, the burning rate of pulverized coal at an outlet of a hearth is relatively high, and emission of pollutants such as the nitrogen oxide content and the sulfur dioxide content meets the environmental protection requirements.