The invention provides a polyoxyethylene sulfonate type dimeric surfactant and a preparation method thereof. The structural formula of the polyoxyethylene sulfonate type dimeric surfactant is shown as a formula I, wherein n is equal to 6, 7, 8, 9, 10, 12 or 14; m is equal to 4, 5, 6, 7, 8, 9, 10, 15 or 20. The preparation method of the polyoxyethylene sulfonate type dimeric surfactant provided by the invention has the advantages of readily available raw materials, mild reaction conditions and simple preparation process, the prepared polyoxyethylene sulfonate type dimeric surfactant is high in purity and high in yield, has excellent salt resistance, high temperature resistance and other physical and chemical properties, and is capable of effectively improving the crude oil recovery rate when being applied to mining of high-temperature high-mineralization-degree complicated reservoir, thereby havingwide application prospects in the field of oil exploitation. The structural formula is as shown in the specification.