The invention discloses a red clay phosphorus adsorbent which comprises, in parts by weight, 115-145 parts of red clay particles, 20-30 parts of diatomite, 10-15 parts of glass powder and 3-10 parts of marble powder. The preparation process comprises the steps: preparing the red clay particles, weighing the raw materials, crushing, calcining, mixing and the like. The red clay has good phosphorus adsorption performance, and has the advantages of rich resources, wide distribution range and low cost; meanwhile, the red clay is a natural environment-friendly material, and does not cause secondarypollution and other problems after being put into sewage bodies, so that the red clay has great development potential in the aspect of phosphorus adsorption.