Abstract: Related are a high-molecular weight allyl alcohol polyoxyethylene polyoxypropylene ether and a preparation method. During preparation, an allyl alcohol raw material and a supported catalyst Rb-NHPA are firstly added into a high-pressure reaction kettle, and it is heated after being replaced with a nitrogen gas; then after the internal temperature of the reaction kettle is raised to a reaction temperature, an ethylene oxide (EO) and propylene oxide (PO) mixture is continuously fed for a reaction; and finally, after the internal temperature of the reaction kettle is reduced, an acetic acid is dropwise added into the reaction kettle so that the crude product of the high-molecular weight allyl alcohol polyoxyethylene polyoxypropylene ether is neutralized to be neutral. The refining process of a polyether is omitted, the process flow is greatly simplified, and the process time is effectively saved. In addition, the supported catalyst Rb-NHP may be recycled.