The invention relates to the technical field of oily alkaline sewage and discloses a fly ash particle composite adsorbent as well as a preparation method and an application method thereof. The fly ash particle composite adsorbent is prepared from the following raw materials: fly ash, acrylamide, acrylic acid, attapulgite, nitric acid, ferrous sulfate and water. The fly ash particle composite adsorbent disclosed by the invention has the advantages of easiness in preparation, convenience in use and low cost and is an environment-friendly product; the performance is obviously better than that of existing conventional active carbon particle adsorbents; and the fly ash particle composite adsorbent has strong adaptability to the oily alkaline sewage, is particularly used for treating the oily alkaline sewage in a crude oil processing process, and can improve the treatment effect on the oily alkaline sewage so as to meet the environmental protection requirement of crude oil deep processing development.