PURPOSE: To prepare the titled compound useful as an intermediate of agricultural chemicals, pharmaceuticals, perfumes, etc., in high yield, without using phosgene, by reacting trichloromethyl chloroformate with a mercaptan in the presence of a dehydrochlorination agent.

CONSTITUTION: The objective compound can be prepared by reacting trichloromethyl chloroformate with a mercaptan in a solvent such as ethyl ether, toluene, chloroform, etc. in the presence of a dehydrochlorination agent (e.g. triethylamine, pyridine, dimethylaniline, etc.) at -10W+60°C, preferably -5W+40°C for 0.5W12hr. The amount of the mercaptan is 0.5W10mol, preferably 1W5mol per 1mol of trichloromethyl chloroformate, and that of the dehydrochlorination agent is 0.1W10mol, preferably 0.5W5mol per 1mol of the mercaptan.