Four Chinese 350°C+ reduced crude feedstocks were heated thermally in the presence of a contact material at 480–540°C in a fixed bed reactor. The feed and products were fractionated into eight fractions using normal pentane precipitation and alumina adsorption chromatography and average molecular parameters calculated with a modified Brown-Ladner method. The results obtained show that the conversion of various fractions of the reduced crudes was quite different. The conversion of asphaltic substances was much higher than those of saturates and aromatics. It is shown that the CH2/CH3ratio, aromaticity and the numbers of aromatic, naphthenic and total ring of heavy products were obviously lower than those of reduced crudes. The effect of temperature on metal, sulfur, nitrogen removal has been also investigated. The data indicate that the removal of weak polar non-porphyrin nickel was larger than that of middle and strong polar nickel complex.