A method for preparing high performance polysilicate ferric aluminum sulfate from coal gangue aims to provide a method for preparing the high performance polysilicate ferric aluminum sulfate from the coal gangue as a main raw material, and provides a new approach for efficient intergraded recycling utilization of the coal gangue, and a new the technology for an iron and aluminum inorganic polymer flocculant is explored. Industrial sulfuric acid and the coal gangue by leached in an acid to obtain ferric aluminum sulfate, the ferric aluminum sulfate is oxidized and polymerized to obtain poly ferric aluminum sulfate, active sodium silicate is obtained from leaching residue by alkali leaching, the poly ferric aluminum sulfate and the active sodium silicate are added for compounding and copolymerization in accordance with the volume ratio and different mass concentrations to obtain a polysilicate ferric aluminum sulfate product after copolymerization for 1-3H. The comprehensive utilization of the coal gangue is complete, the prepared product has high added value, the method has the advantages of convenient operation, low energy consumption, simple process, and the like, can solve the problem of high turbidity, high chroma and high heavy metal residues and the like of all kinds of wastewater, and the wastewater can meet national emission standards.