A mechanistic study of the reaction H+HCNO, in which the products Pi with i=1,2,3,4 are involved, is carried out with CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p)+ZPVE to determine a set of reasonable pathways. It is shown, from the potential energy surface, that the P1(HCN+OH) is the major product channel, with a minor contribution of both P2(CO+NH2) and P3(CH2O+N), whereas the P4(CH2+NO) is less favorable. The present work can provide some useful information for the experimental studies.