The invention discloses a preparation method for a double quaternary ammonium cation Gemini surfactant, and a water injection well pressure-reducing injection-increasing surfactant solution containing the double quaternary ammonium cation Gemini surfactant and a preparation method thereof. The preparation method for the double quaternary ammonium cation Gemini surfactant comprises the following steps: in a solvent, executing the solution polymerization reaction by dodecyl dimethylamine and dodecanol glycidyl ether, and executing the backflow reaction for a while. The water injection well pressure-reducing injection-increasing surfactant solution containing the double quaternary ammonium cation Gemini surfactant comprises 30-40 parts of the double quaternary ammonium cation Gemini surfactant by mass prepared according to the method and 70-60 parts of water by mass. The method for preparing the water injection well pressure-reducing injection-increasing surfactant solution comprises the following steps: stirring and mixing the double quaternary ammonium cation Gemini surfactant and the water. The water injection well pressure-reducing injection-increasing surfactant is capable of remarkably reducing the oil-liquid interfacial tension, and reducing the water injection pressure, and has certain ability to change rock wettability.