The invention discloses a garbage permeate wastewater treatment agent based on modified fly ash and a preparation method. The composition comprises the following raw materials in parts by weight: fly ash fine powder 50-60, sodium bicarbonate 8-10, Polydimethyldiallyl ammonium chloride 11‑17, cationic polyacrylamide 9‑10, hydroxymethyl chitosan 10‑20, chitosan quaternary ammonium salt 10‑20, montmorillonite powder 20‑24, biological Sludge 6-10, magnetized tourmaline powder 12-15, basic alumina 8-10, loofah 40-50, appropriate amount of ethanol, appropriate amount of deionized water, appropriate amount of water. The present invention uses sodium bicarbonate to pretreat the coal ash powder, which improves the pore size and surface area ratio of the coal ash powder, and then further composites and modifies the activated composite powder to improve the adsorption efficiency. The present invention also realizes the coal ash powder The advantages of high-capacity, easy-to-separate, and easy-to-recover adsorbents.