we calculate the equilibrium geometry structure of OCN2 by using B3LYP, B3p86, B3pw91 and MP2 methods combining? with cc-pVnZ (n=D,T) and aug-cc-pwCVDZ basis sets. On this base, we obtain the spectroscopic constants and anharmonic force field of OCN2. Then we compared the results of equilibrium geometry structures, rotational constants, vibration-rotation interaction constants that we obtained from the calculation with the relevant experiment and theoretical data. In addition, we also predict the quartic and sextic centrifugal distortion constants, coliolis constants, third-order and forth-order force constants of OCN2.
