Heterogeneous condensation of water vapor on coal-fired fine particles was investigated in a growth tube. The influence of operating parameters and wetting agent addition on vapor condensation enlargement for three coal-fired fine particles from different power plants were tested. The results show that all the three coal-fired fine particles induce heterogeneous condensation and the process is favored by increasing the water temperature and residence time and decreasing particles initial number concentration; wetting agent addition highly facilitates the effect of vapor condensation on fine particles and the performance is increased with the increase of wetting agent addition. It is also found that excessive addition encourages the performance of final mean size of particles but discourages the performance of finer particles enlargement. With wetting agent addition, the mean diameter of fine particles can be enlarged above 3 mu m while the mean diameter can only be enlarged above 2 mu m without wetting agent addition (the original mean diameter of particles is about 0.15 mu m).