Abstract: Analysed in this paper are the soot formation, its types and components in the heater for oil transmission pipeline system. It is believed that the soot consists of residual nonflamable salts and foreign matters in the fuel, such as Na, K. V, Mg, and some flamabble particles left due to incomplete combustion. It is pointed out that the soot volume depends greatly upon ash content in the fuel, the performance of burner nozzle, air temperature, and burning operation. General soot forming regulations are summarized for radiant coils and convection coils. It is concluded that the coating on coils will result in poor heat conduction, low burnung efficiency and low burner performance due to the increace of the resistance against flue gas re-circulation; aggravation of dew point corrosion and short heater service life. Suggested are the following mesures against soot formation; periodical manual cleaning, installing a soot blower in convection box. installing a soot door in convection box. selecting burners with better atomization. installing a fuel filter in the upstream of the burner.