The solidified sludge as a new type of liner material should be at the bottom of municipal solid waste landfill site to prevent the contamination of the pollutant leakage. The hydrodynamic dispersion test was conducted to investigate the postponing effect of solidified sludge. It was very difficult to obtain hydrodynamic dispersion parameters of sludge solidified layer with low permeability by the existing column tests and methods. The flexible wall parameter was proposed and improved to solve the problem. Because of the high concentration and strong penetrating power, fluorine ion was chosen as the typical representative. The hydrodynamic dispersion parameters could be calculated by the breakthrough curve of fluorine ion. And then, the two dimentional definite method was used to analyze the transference scope and concentration distribution of fluorine ion in solidified sludge layer and surrounding in 60 years. The situation without solidified sludge layer had a contrast with the above. The results showed that the solidified sludge layer had an important postponing effect on the transference of fluorine ion. Because positive pollutants had weaker penetrating ability than negative ones. The solidified sludge also had a strong blocking effect on the positive pollutant such as heavy metals or other positive pollutants, which could further delay the pollution of landfill leachate.