The rates of dissolution of domestic limestones in the wet type flue gas desulfurization process were measured and the effects of particle size distribution and composition of limestone through the limestone reaction were studied. Five domestic limestone samples of different size distribution(325, 200 and mesh)were tested in both batch and continuous apparatuses. The limestone dissolution rate data measured in the batch experiment system indicated that limestone dissolution rate can be improved by small limestone particles. Realative ranking of limestone dissolution rate was 325 mesh>200 mesh> 100 mesh. At a fixed size of limestones, the dissolution rates were affected by the compostition of limestone, especially MgO. The rates were improved two times by limestone of 3% MgO than pure limestone. But the compostion effects to the dissolution rates were reduced as increasing the size of the particles. The continuous type experiments also showed that more limestone was dissolved as the size of limestone decreased.