Special attention is required on the fine particle control after desulfurization because a large quantity of fine particles are emitted into the atmosphere from the coal-fired power plants. In an attempt to figure out the transformation of fine particles during the limestone gypsum desulfurization, the physical properties of fine particles before and after the desulfurization system were measured in a power plant. Moreover, the investigations on the removal and formation characteristics of fine particles during the desulfurization process were carried out in a pilot plant. The results showed that the particle characteristics changed after desulfurization and new particles of CaSO4 may be generated. The scrubbing of the desulfurization slurry generated large numbers of fine particles, which were mainly located in the sub-micrometer range, and the inlet SO2 concentration had little influence on the fine particle formation. Besides, the desulfurization slurry characteristics were closely related to the concentration and size distribution of fine particles after desulfurization. With the lower proportion of fine particles and the decrease of the solid mass concentration in the desulfurization slurry, the generated fine particles were reduced. The fine particle emission can be controlled by the adjustment of operation parameters. With the decrease of the gas flow velocity and the liquid/gas ratio, fewer droplets of the desulfurization slurry were entrained out of the scrubber, resulting in the corresponding decrease of fine particle concentrations after desulfurization.