The invention discloses a preparation method of an emulsifier for electric blasting. The method comprises the following steps of: stirring sorbitol, adding an aqueous phosphorous acid solution and heating the mixture to 115-150 DEG C; adding 500-530kg of oleic acid into a reactor, and stirring the mixture; slowly adding an aqueous sodium hydroxide solution into the reactor and quickly heating the reactor to 210 DEG C; maintaining the temperature of the reactor for 3 hours; sampling, stirring the mixture and assaying the acid value, the specific viscosity and a measured hydroxyl value; when the vacuum pressure reaches 0.06-0.11MPa, filtering the mixture in vacuum, standing for 10-12 hours and cooling; and uniformly mixing lecithin and T-152 emulsifier. In the method, mixed hydramine in a proper proportion is selected to react with carboxylic acid, thereby the steric effect in the reaction is reduced, and the emulsifier can obtain larger hydrophilic groups; and moreover, the hydrophilic groups have stable property so that the property stability of powdered emulsion explosives in the processes of production and storage is improved.