Abstract: In order to solve the potential problem of waste liquid produced in the process of extracting aluminum and silicon from coal gangue,the waste liquid is used as a raw material to prepare free fired bricks which is a promising way of treatment. The effects of adding the aluminum and silicon extraction waste liquid on the main performance indexes of free fired brick,such as compressive strength,frost resistance and water absorption were studied and analyzed; the interal mechanism of the influence of aluminum and silicon extraction waste liquid on the above parameters were explained by SEM and XRD analysis. The result shows that when the waste liquid of aluminum and silicon extraction from coal gangue is used to prepare unfired brick,the compressive strength of the brick can be reduced by adding waste liquid. The compressive strength of unfired brick is 23.75 MPa,reduced by 4.93 MPa when adding 50% waste liquid as a substitute of water,and the compressive strength is 21.34 MPa,reduced by 7.34 MPa when the content is 100%. The salt ions in the waste liquid seep to the brick surface and the pores are formed during this process. Moreover,softer anhydrite and calcite appear with the addition of waste liquid,which can lead to the decrease of compactness and compressive strength of free fired brick. In the frost resistance tests,when the content is 50%,the strength loss rate of the free fired brick after 15 freeze-thaw cycles is 2.82%,and the mass loss rate is 0.35%;when the content is 100%,the strength loss rate after 15 freeze-thaw cycles is-28.12%,and the mass loss rate is 0.76%. Based on the dual effects of waste liquid,the positive effect of 100% waste liquid is exerted completely in tests,resulting in the increase of compressive strength instead of decreasing. In the water absorption tests,when the content is 50%,the water absorption rate is 28.29% after soaking for24 h; when the content is 100%,the water absorption rate of free fired brick is 29.99% after soaking for 24 h. The water absorption rate of free fired brick increases with the addition of waste liquid of aluminum and silicon extraction from coal gangue.