New reactions of Lawesson reagent (LR) with a-hydroxy (amino)nitriles have been studied. The experimental results showed that the five-membered phosphoroheterocycles 2 and 4 bearing N-P-N or S-P-N moiety could be readily prepared in high yields. Meanwhile, the possible mechanism of the reactions was also discussed. New reactions of Lawesson reagent (LR) with a-hydroxy (amino) nitriles have been studied. The experimental results showed that the five-membered phosphoroheterocycles 2 and 4 bearing NPN or SPN moiety could be prepared prepared in high yields. Meanwhile, the possible mechanism of the reactions was also discussed.