Abstract: Karst is widely distributed in China. The numerical simulation is often used to study the development and change of karst fractures. The expression of different dissolution rates has a great influence on the results of the numerical model. In order to compare the effects of dissolution rate equations under different mechanisms, such as surface reaction and diffuse migration and their combination, we took the single fracture of limestone parallel plate as an example to establish models of coupled fracture flow and chemical dissolution with different dissolution rates. The analysis results show that when the reaction rate is determined by only one factor, the dissolution depth is shallower and the dissolution amount and fracture flow is smaller. Especially the critical point lagged behind the one that is determined by two factors. From long term view, the results of two different models would be more distinguished, so we should select the appropriate dissolution rate model based on actual condition.