In the presence of cesium hydroxide, the reaction of O,O-diethylphosphonate with alkynylselenides at room temperature does not provide the expected additional product by using dimethyl formamide (DMF) as the solvent, but rather causes the cleavage of Se-Csp bond and gives the corresponding terminal alkynes and Se-aryl phosphoroselenoates in 89~95% yields. The influence of substituent at the alkynes and selenium atom on the reaction was investigated, and the results showed that the reaction was not sensitive to the electronic nature. The reaction mechanism was that O,O-diethylphosphonate reacted with cesium hydroxide to produce (EtO)2P-(O)Cs+, which underwent nucleophilic attacks on alkynylselenides to produce Se-aryl phosphoroselenoates and RC≡C-Cs+. The latter was hydrolyzed in the presence of water to form terminal alkynes and catalyst cesium hydroxide. The method could provide a new and simple path for the cleavage of Se-CsP.