The invention discloses a preparation method of an N-hydroxyurea compound, which specifically comprises the following steps: step 1, sequentially carrying out Lossen rearrangement and nucleophilic reaction under the action of alkali by taking Boc NHOH as shown in a formula 1 as an initial reactant, SO2F2 gas as an acylating agent and an amine compound RR 'NH as a nucleophilic
reagent to obtain a tert-butoxyurea compound as shown in a formula 2; and 2, removing the tert-butoxy group from the tert-butoxyurea compound to obtain the N-hydroxyurea compound as shown in a formula 3. The innovation point of the invention is that commercialized easily available gas
sulfonyl fluoride promotes Lossen rearrangement of tert-butylhydroxylamine to generate a key intermediate tert-butoxy
isocyanate, the key intermediate tert-butoxy
isocyanate and a substrate amine compound are subjected to a one-pot reaction to obtain the N-hydroxyurea compound, the
reaction conditions are simple, the operation is convenient, the compatibility of substrate functional groups is strong, and the application prospect is good.