Method of preparing trialkoxysilanes isocyanic ester

The invention discloses a preparation method of trialkoxy siloyl isocyanate, comprising the following steps: (1) chlorine catching agent is dissolved in water and then is added into a reaction device to be stirred, wherein, the temperature is controlled at -5-0 DEG C; (2) triphosgene and trialkoxysilane amine are respectively dissolved in organic solvent and then respectively added into the reaction device and react by stirring for 10-20min, wherein, the temperature is controlled at -5-10 DEG C; (3) the phase separation is carried out on the reacted solution, the organic solvent is used for extracting water phase for 1-3 times, the drying is carried out after organic phases are annexed, and the organic solvent is extracted, filtered and removed; (4) after the vacuum distillation, the trialkoxy siloyl isocyanate is obtained. The chlorine catching agent used by the invention has the advantages of cheap price and low production cost. The used triphosgene has the advantages of no toxicity, safety and reliability.