The invention discloses a continuous oil pipe inner antiseptic treatment agent and a preparation method thereof. The treatment agent comprises mineral oil, preservative, solubilizer, film forming assistant, a penetrating agent and an anti H2S/CO2 corrosion inhibitor; and according to 100% of the weight of the treatment agent, the weight of the mineral oil is 70-80%, the weight of the preservativeis 3-15%, the weight of the solubilizer is 2-6%, the weight of the film forming assistant is 2-6%, the weight of the penetrating agent is 2-4%, and the weight of the anti H2S/CO2 corrosion inhibitor is 1-3%. The preparation method comprises the following steps: the mineral oil, the preservative, the solubilizer, the film forming assistant, the penetrating agent and the anti H2S/CO2 corrosion inhibitor are mixed and stirred uniformly to obtain the treatment agent. The invention further discloses a construction method of the continuous oil pipe inner antiseptic treatment agent. The continuous oil pipe inner antiseptic treatment agent has the advantages of excellent corrosion resistance, safety, environmental protection, high weather resistance and stable performances.