Petrographic analysis can provide valuable information about pulverized coal used in coal-fired power plants. In this study, petrographic analysis was used to determine the effect of blending on the combustion of low-rank coal from Mongolia and two bituminous coals from Russia. After blending these coals based on their calorific values and combusting them in a drop tube furnace, the unburned combustibles in the char were analyzed. The coal rank, determined from the mean random vitrinite reflectance, was closely correlated with the proportion of each single coal in the blend. Char component analysis showed that the generated char particles were not affected by the coal rank but had a strong relationship with the microlithotype of the raw coal. In contrast, for single coals, the unburned combustibles at equal temperatures were affected by the coal rank. Morphological analysis of the char types revealed that the geometric tendency of each coal was in agreement with the char formed at different temperatures. However, combustion results for the blended samples exhibited somewhat complicated tendencies. The unburned combustibles showed interactions between coals relating to their petrographic properties, such as vitrinite reflectance and char components.