The removal efficiency of PM2.5 is very low in traditional dust removal devices, especially for the particles range from 0.1 to 1 mu m, which can decreases to 25% and pretreatment must be conducted before fine particles enter into these devices. Vapor condensation on fine particles can improve the PM2.5 removal efficiency of traditional devices. Therefore, a novel process was proposed for heterogeneous condensation on fine particles of water vapor with partial gas circulation in this paper. The essential supersaturation was established by adding hot water into cooled saturated gas, and the application of partial gas circulation technique in this process made the required supersaturation level decreasing. The fine particles were enlarged by the heterogeneous condensation and the collision-coalescence of droplet and particle in the partial gas circulation growth tube (PGCGT). The results indicated that the enlargement of fine particles in the PGCGT was more efficient than that in the conventional growth tube (CGT). The performance of fine particles enlargement by this process was influenced by many factors, such as circulation point at the growth tube, gas circulation proportion, supersaturation and initial particle concentration in the gas flow. Under the optimum conditions, the arithmetic mean diameter of the submicron particles could be enlarged to 6.156 mu m. Moreover, the different growth pathways of particle enlargement in the PGCGT were elucidated.