The invention discloses a fly ash based composite material, which is prepared from fly ash and zinc hydroxide or zinc oxide coating the surface of the fly ash. The fly ash based composite material is a material of a core-shell structure using the coal ash as a core and using the zinc hydroxide or zinc oxide as a case; the fly ash based composite material has good whiteness; the application range is greatly expanded; the antibacterial activity value is high; the durable antibacterial performance of the zinc oxide is good; the fly ash based composite material can be used for preparing an antibacterial coating; the coating stability is high. The raw material cost is low; the waste material reutilization can be realized; the added value of the fly ash can be greatly improved; the application prospects are very good.