Abstract: Using 4 inferior residual oils as raw materials, the effect of feedstock properties on the characteristics of coke formation during initial thermal conversion process was studied.The results show that the influence for coke induction period of different oils affected by temperature can be measured with the sensitivity parameters.The shorter the coke induction period of the residue, the bigger the sensitivity parameter.The coke induction period has a higher decrease rate with the reaction temperature rising.The coke formation property generally depends on feedstock's basic properties, and the influence of various properties of inferior residual oils on coke formation is different under the same reaction conditions.Carbon residue, ash, relative molecular mass, asphaltene precipitation onset point and stability parameter have strong correlations with the coke induction period, especially for the colloidal stability of oil reflected by asphaltene precipitation onset point and stability parameter.The colloidal stability of the inferior residual oils is related to the coke formation characteristics.The worse the stability of the residue, the more likely the coke is to form.The coke forming process is a gradual destruction of the colloid system during thermal reaction.