Abstract: Coaltar pitchbased carbon microspheres were prepared by adding petroleum pitch using emulsifying pitchtoluene colloidal solution in polyvinyl alcohol (PVA) glycerol solution. To clarify the influence of pitch solubility in toluene and its affinity with the hydrophobic methylene groups of PVA on the sphere formation, petroleum pitch having a high affinity with methylene groups was added to the coal tar pitch in different proportions. A model was proposed to tentatively elucidate the sphere formation mechanism. It was found that petroleum pitch addition could improve the sphericity of pitch spheres by stabilizing the surfactant orientation on the interface between pitch molecules and dispersant. Adding petroleum pitch lowered the softening point of mixed pitch and an appropriate amount of addition was needed to ensure a high softening point of mixed pitch spheres above the reaction threshold temperature for airoxidative stabilization.