The invention discloses a silthiopham key intermediate preparation method which includes the steps: taking trimethylsilyl propiolic acid, thionyl chloride and allyl amine with the mole ratio of 1:1.5:1-1:2:1; dissolving the trimethylsilyl propiolic acid in a solvent and dripping catalysts; dripping the thionyl chloride in ice bath; stirring solution at the temperature of 0-25 DEG C; distilling the solution to obtain residues, dripping allyl amine into the residues in ice bath and performing reaction; extracting and drying the solution to obtain trimethylsilyl propioloyl allyl amine. The mole ratio of the catalysts to the trimethylsilyl propiolic acid ranges from 1:100 to 5:100, the solvent is one or more of methylbenzene, dichloromethane and methylene diethyl ether, and the catalysts are one or more of N, N-dimethylformamide and hexamethylphosphoric triamide. The method is simple in raw material and reaction process, environmentally friendly, safe, short in reaction time and high in target product yield, production cost is reduced, atom economy is good, the concept of green chemistry is met, and the method has great competitive advantages and industrial production use values.