In a hydrocarbon well with water injection agent

The invention relates to a reinjection water treatment agent for an oil well. The treatment agent comprises: 15-65 parts by weight of an oxidizing bactericide, 12-34 parts by weight of a flocculant, 5-12 parts by weight of an iron ion complexing agent, 15-24 parts by weight of a corrosion inhibitor, and 15-40 parts by weight of a surfactant. According to the invention, problems occur in present reinjection water treatment processes are solved, complicated construction programs of the present water treatment processes are avoided, treated reinjection water accords with relevant standards and satisfies needs of the engineering, the treatment agent of the invention has a very broad application prospect.