The infra-red spectra of three Chinese vacuum residua and their SARA fractions, together with their average chemical structure parameters obtained from elementary analyses, molecular weight determination and H-1 NMR measurement, have been employed to elucidate, to some extent, how the colloidally dispersed mixed asphaltenes-heavier resins clusters in the three typical Chinese petroleum vacuum residua, Daqing, Shengli and Gudao vacuum residua, are formed. It has been concluded that formation of the mixed clusters arises from the aromaticity-promoted hydrogen bonding interaction.