To investigate the effects of permeability and thickness of materials under different loads on the pollution prevention capacity of a cutoff wall, contaminant transport was calculated based on analysis of the engineering properties of the soil-bentonite cutoff wall, and the breakthrough time of the cutoff wall was analyzed under different pressures and boundary conditions. Results indicate that soil-bentonite has a moderate level of compressibility, and the difference between the hydraulic conductivities at the top and bottom of the cutoff wall may reach one order of magnitude. There is a large difference in the breakthrough time calculated with two standards, i. e. , the relative pollutant concentration reaching 10% and the stable pollutant flux reaching 5%, with the ratio of calculated breakthrough time ranging from 1.42 to 2.21. The pollutant flux and relative concentration downstream of the cutoff wall calculated with parameters of the bottom of the cutoff wall are less than those calculated with the initial parameters, and the corresponding breakthrough time of the former is longer than that of the latter. According to the results obtained with the parameters under the maximum pressure, the designed cutoff wall will be dangerous.