Abstract Dense pyrolyrical carbon layer is anther indispensible layer of coated fuel particle of high temperature gascooled reactor.The function of dense pyrolytical carbon layer in coated fuel Particle and the properties needed are introduced.The relation between pyrolytical temperature and the density, deposition rate and deposition efficiency of the pyrolytical carbon obtained is investigated. The temperature range for obtaining dense pyrolytical carbon layer with density of1.90±0.10g/cm ̄3 is between 136...