AbstractPotential energy surface of HNOS system is investigated by means of MP2 method with 6–311 ++ G(d, p) basis set. The energy for each minimum and saddle point on the potential energy surface is corrected at the QCISD(T)/6–311 ++ G(3df, 2p) level of theory with zero‐point vibrational energy included. As a result, eighteen isomers are theoretically predicted andcis‐HNSO is found to be global minimum on the potential energy surface. Wherein, fourteen isomers are considered as kinetically stable species, and should be experimentally observed. Comparisons are made for HNOS system with its analogues, HNO2and HNS2. The nature of bonding and isomers'stability of HNOS system are similar to HNS2. The obvious similarities and discrepancies among HNOS, HNO2and HNS2are attributed to the hypervalent capacity of sulfur, oxygen and nitroge