The invention discloses a sewage treatment agent which comprises the following components in parts by weight: 20-60 parts of polyacrylamide, 10-30 parts of organic amine, 10-20 parts of sodium hypochlorite, 2-10 parts of a composite antisludging agent, 1-8 parts of an inorganic corrosion inhibitor and 1-10 parts of acetic acid. Compared with the prior art, the sewage treatment agent has the benefits that the formula comprises a flocculant, an adsorbent, a sterilizing agent, the antisludging agent, the corrosion inhibitor and a disincrustant, so that the water is comprehensively treated. The sewage treatment agent has the advantages that (1) the treatment scope is wide and the removal rate is remarkably increased; (2) the treatment effect is excellent, and the removal rate of suspended solids is up to be more than 90%; (3) the dewatering of the sludge is easy, a flocculating constituent is dense and is settled rapidly because of the used unique material, and the produced sludge is dewatered easily; (4) the cost of the materials is low, the sources of the materials are wide, the amount of the material used is low, and the advantage of low cost is achieved; (5) the sewage treatment agent is non-toxic, harmless, and easy to store.