Abstract: This paper reveals the dissolution gritty mechanism of dolomite. Some dissolution tests are carried out under different solution conditions and dolomite structures to analyze the factor of dissolution rate. It uses the casting thin sections and the scanning electron microscope methods to analyze the microstructure of dolomite at different dissolution stages.the test findings are that: (1)the rock microstructure dominates dissolution rate. The relations of different dolomite structures with its dissolution rate rateare as follows: (a) the dissolution rates for medium-fine grain dolomite, fine-powder crystal dolomite and powder dolomicrite are greatest and medium and lowest, respectively; (2)Specific surface area is connected with the total dissolution amount but not the dissolution rate in unit area; (3)the dissolution starts at the inter grain, the inter crystal void, the tectonic micro-fracture and the cleavage. It extends gradually to make sure that the voids and fractures are connected each other; (4)the dissolution worsens the microstructure of Dolomite gradually, weakens the connecting force of crystals. It couples with the disintegration and falling off of crystals. And finally it breaks up into fine particles and results in the gritting of dolomite.