The effect of the content changes of WC, YG8 and 663-Cu on the bending strength of the WC based composite is investigated by the mixture design. The content changes of the three components have significant effects on the bending strength of the matrix with or without diamonds, and the effects exhibits linear model relations. The related regression equations are obtained, and the order of the effect of the results is as follows: YG8＞WC＞663-Cu. Besides, the content changes have less effects on the bending strength loss rate, indicating that the diamond retention cannot be effectively improved by adjusting the proportion of WC, YG8 and 663-Cu in WC based composites.