In conjuction with aerosol dynamics theory and by incorporating complex gas phase and particulate phase chemistry, sectional soot models can provide a detailed description of soot particle structures formed in a combustion environment. A recently developed moving sectional approach has been improved in this study to provide a more accurate description of the soot particle size distribution. The soot prediction for a Plug Flow Reactor ( PFR), which is fueled by an ethylene/ air mixture ( with the equivalence ratio of 2.2), has been compared with experimental data and simulation results provided by both the conventional fixed sectional approach and the method of moments model. The soot inception, surface growth/ oxidation, and polycyclic aromatic hydrocarbon ( PAH) condensation submodels were based on a previous study and coupled with a detailed reaction mechanism of C2 hydrocarbons. The results show that the improved moving sectional approach calculated a particle size distribution which was in good agreement with the fixed sectional approaches with finer grids, but required less CPU effort ( less than 50%). The computed particle size distributions were validated by experimental data. The soot mass concentration and total number density predicted by three sectional approaches have been compared with the method of moments model for different simulation cases and it shows that the four numerical methods of aerosol soot model provided consistent results.