The synthesis of 5-chloro-2-methyl-4-isothiazoline-3-ketone with multisodium sulfide, methyl acrylate, methyl amine, had been studied. The product had good ability of killing the mold and bacteria.

The invention discloses a detergent, which is sodium salt containing 5-chloro-2-methylisothiazolone dissolved in organic solvent or 5-chloro-2-methylisothiazolone dissolved in water.