Mechanisms of the addition, elimination, and migration of ethynyl radical (C2H) with n-propylcyanua (C3H7CN) pave been studied by using Density-Functional Theory. The BHandHL YP functional was carried out with the 6311 ++G( d,p) and 6-311 ++G(3df,2p) basis sets. Geometry optimizations were performed with the former basis set while single-point calculations were done with the latter basis set in order to improve the energies. The relative energies were corrected with zero-point energy (ZPE). Based on the computational results, the authors constructed the potential energy surface for the reaction of C2H with C3H7CN. This potential energy surface, in combined with the thermodynamic quantities, allows predicting the high ability to form C3H6, C3HN, and cyclo-C3H6 in the title reaction. Particularly, the computational results show that the formation of product PR19 (C3H7 + HCCCN) is the most favorable channel of this reaction. These results are useful to understand the reactivity of ethynyl radical with n-propylcyanua and also with other nitrile derivatives.