The invention discloses a method for treating antibiotic wastewater by using a graphdiyne modified silver phosphate composite photocatalyst, and the method comprises the following steps: treating theantibiotic wastewater by using the graphdiyne modified silver phosphate composite photocatalyst, wherein the graphdiyne modified silver phosphate composite photocatalyst adopts graphdiyne nanosheets as a carrier, and silver phosphate particles are loaded on the graphdiyne nanosheets. In the method, the adopted graphdiyne modified silver phosphate composite photocatalyst has efficient catalytic activity, can degrade and remove antibiotics in the water body under visible light in a short time, has the advantages of low cost, high treatment efficiency, good removal effect and the like, and has avery good application prospect. Taking norfloxacin as an example, when the graphdiyne modified silver phosphate composite photocatalyst is used for degrading norfloxacin wastewater, the norfloxacin wastewater can be completely degraded and removed after illumination for 12 minutes, the treatment efficiency is high, and the treatment effect is good.