The invention discloses a coking coal blending method of improving homogeneity coefficient of coke size. The method comprises the following steps: determining the average maximum reflectivity, the solid-soft temperature interval region, the Gieseler fluidity and the coking optical organization structure of a single coal vitrinite; according to a test result, selecting the type of coal in percentage by weight of 15-18%, wherein formula is greater than or equal to 2.0% and the coking optical organization structure is 100% an inertial component; smashing till the part with particle size less than or equal to 0.4mm is over 90%; 2) selecting the type of coal in percentage by weight of 30-40%, wherein formula is 0.6-1.1%, the solid-soft temperature interval region is greater than 95 DEG C, the maximum Gieseler fluidity log value logMF is greater than 4 and the inertial component of the coking optical organization structure is less than or equal to 25%; 3) selecting the type of coal in percentage by weight of 20-40%, wherein formula is 1.1-2.0% and the granular inlay component of the coking optical organization structure is greater than or equal to 60%; and 4) selecting the type of coal in percentage by weight of 20-60%, wherein formula is 1.1-2.0% and the granular inlay component of the coking optical organization structure is greater 20-60%, and blending coal according to a certain proportional range. According to the coal blending method disclosed by the invention, the coke is uniform in grain size, high in cold and heat state strengths and low in coal blending cost.