The invention relates to CO2 activation and conversion and related chemical technical fields, and specifically relates to a synthesis method of propiolic acid compounds. The method is characterized in that in the presence of an added additive and alkalis, terminal alkynes directly react with CO2 to generate propiolic acid compounds. The proper terminal alkyne substrate may be phenyl acetylene, substituted phenyl acetylene, heterocyclic aryl alkynes, or aliphatic terminal alkynes. Compared with the prior art, the invention mainly provides a novel and simple reaction system. According to the preparation method, potassium carbonate is taken as the alkali, quaternary ammonium salts are taken as the additive, and acetonitrile, which is convenient for the post treatment, is taken as the solvent. The preparation method is reported for the first time. The reaction system does not need any transition metal catalyst; the experiment operation is simple; the raw materials are cheap and easily available, and the preparation method is environment-friendly and generates great application value, social benefits, and economic benefits.