The invention relates to a preparation method of a multifunctional slick water fracturing fluid drag reducer. The preparation method comprises the following steps: applying inverse emulsion polymerization reaction for compounding two non-ionic emulsifiers into a compound emulsifier, dissolving the compound emulsifier in an oily medium in the mass fraction of 0.3%, stirring for 1-2 hours under the protection of nitrogen, then adding 0.3% by mass fraction of a hydrophobic monomer, then adding 0.3-0.5% by mass fraction of a chelating agent and monomer solution of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, starting to heat, and after temperature is increased to 52-57 DEG C, adding an oil soluble initiator and a water soluble initiator in batches, and carrying out heat preservation for 8-10 hours after the initiator is completely added, so that stable water-in-oil type polymer emulsion is obtained finally. According to the invention, an inverse emulsion polymerization method is utilized, and by introducing special functional group substances and emulsifiers, a slick water drag reducer with anti-drag and discharge assisting functions is developed, slick water cost is reduced, more importantly, fluid preparation time is shortened, a fluid preparation procedure is simplified, and construction efficiency is greatly improved.