A detailed heterogeneous kinetic mechanism based on elementary surface reactions has been developed to model pyrocarbon deposition obtained by propane pyrolysis on carbon fibers. The model contains 275 elementary steps and involving 66 surfaces sites. It is combined with a homogeneous model in order to reproduce both deposition kinetics and gas phase composition. Deposition reactions are assumed to occur on the edges of basic structural units on both zig-zag and armchair sites. The kinetic parameters of surface reactions are estimated by analogy with a chemically similar gas phase “prototype” reaction. Simulated results are compared with experimental results obtained in a perfectly stirred reactor at low pressure (2.6 kPa) with temperature ranging from 1173 to 1323 K and residence time ranging from 0.5 to 4 seconds, using propane diluted in nitrogen as carbon precursor. Results show good agreement between simulations and experiments for both deposition kinetics and gas phase composition. In the chosen conditions, pyrocarbon precursors are mostly small unsaturated species (acetylene and ethylene) and methyl radicals.