To investigate the effects of biochar as a salt-isolation layer in soil, the effect of biochar as a salt-isolation layer was evaluated by comparing the flow rate of subsurface pipe, the conductivity of leachate, the rate of soil desalination, and the efficiency of leaching of the biochar salt-isolation layer to the conventional gravel salt-isolation layer. The results showed that the flow rate of subsurface pipe of the biochar treatment was 16.1% higher than that of the gravel treatment. The leachate conductivity of 0.83 mS/cm could be treated as the theoretical end point of the leaching. Both treatments reached the theoretical end of leaching during the second leaching process, and the time consuming of the biochar treatment reached the theoretical end of leaching was 13.3% shorter than that of the gravel treatment. The soil leaching efficiency of the two treatments were almost the same. The soil resalinization preventing effect of the biochar salt-isolation layer was better than that of the gravel salt-isolation layer. To sum up, the application effects of the biochar salt-isolation layer were better than that of the traditional gravel layer. The research results provided a reference for the engineering application of the biochar salt-isolation layer in saline-alkali land improvement.