Preparation of ethylsulfonyl-methyl cyanide is carried out by: taking acetic acid as reactive solvent, taking hydrogen peroxide as oxidant and oxidizing ethyl phenyl methyl cyanide into ethylsulfonyl-methyl cyanide. It's convenient, controllable and efficient. It has gentle reactive condition, higher content and can be used for industrial production. It can be used to produce super-efficient sulfonylurea herbicide jade pyrsulfogentian intermediate.