The invention discloses a pre-treating agent for a water injection well of a low-permeability reservoir and a manufacturing method of the pre-treating agent, and belongs to the technical field of water injection well development of an oil field. The pre-treating agent comprises the following components, by mass percentage, 0.3-0.8% of a surfactant, 1-2% of ammonium chloride, 2-5% of ethanol, 2-5% of a micro-molecular cationic polymer, 1-5% of ethylene glycol monobutyl ether, 10-15% of hydrochloric acid, 1-3% of hydrofluoric acid, 2-4% of a corrosion inhibitor, and 1-2% of an iron-ion stabilizing agent, with the balance being water. The surfactant comprises, by mass percentage, 75-90% of a fluorocarbon surfactant, with the balance being betaine and/or fatty acid diethanol amide. Components in the pre-treating agent match each other well and can be used at the same time. Through adoption of the pre-treating agent, multiple slugs are effectively form one slug through pre-treatment before casting of the water injection well, and the oil-water interfacial tension is reduced to or below 3*10<-4> mN/m. The water injection pressure is reduced, and the effect of preventing swelling and relieving solid blocking is achieved. Pressure reduction and injection increase are effectively achieved, and the construction efficiency is obviously increased.