The invention discloses a preparation method of a fluorine-containing non-ionic surface active agent and an application. The preparation method comprises the steps of carrying out amidation reaction on perfluoroalkyl sulfuryl fluoride and N, N'-dimethyl (ethyl)-1, 3-propane diamine to obtain an intermediate 1; after refining, adopting acetone as a solvent to react with ethylene oxide or chlorethyl alcohol to obtain an intermediate 2 (N'-3-(dimethyl(ethyl))-propyl-(N-perfluorobutylsulfonyl-N-epoxy)-amine); carrying out ring-opening reaction on the intermediate 2 and ethylene oxide according to different proportions to obtain the fluorine-containing non-ionic surface active agent. The preparation method disclosed by the invention has the advantages that the production cost of the surface active agent is low, the preparation method is simple, the requirement on production equipment is low, and the production process is simple; the yield is high, the fluorine-containing monomer conversion rate reaches 93%; the surface performance is excellent, the lowest surface tension of certain compound to water is below 20mN/m and the HLB (Hydrophile Lipophile Balance) value of the surface active agent is easily changed.