The invention belongs to the field of modification of magnesium oxychloride cement, and particularly relates to a preparation method of high-water proportion phosphorus-containing magnesium oxychloride cement beneficial for increasing the early strength. According to the preparation method disclosed by the invention, proceeding of early hydration reaction of the magnesium oxychloride cement is promoted by adding a specific surfactant during magnesium oxychloride cement slurry preparation, the hydration reaction speed is quickened, the coagulation time is reduced, and higher strength can be obtained by the prepared magnesium oxychloride cement during an early maintenance stage.