Method for preparation of 5-alkylsalicylaldoximes with formula 1, where R is a C6-C16 alkyl group, consisting in that into a water-alcohol solvent system, p-alkylphenol, sodium hydroxide, chloroform and hydroxylamine are introduced, while in relation to the alkylphenol used, sodium hydroxide and chloroform are used in amounts from the stoichiometric amount to a 100% excess, and hydroxylamine is used in amounts from the stoichiometric amount to a 60% excess, and the reaction is carried out at a temperature of 60-75° C. for 1.5-4 h, and then, at a temperature of 20-30° C., the post-reaction mixture is acidified till the pH of the aqueous phase