The equilibrium structure and single-point energy scanning of the ground state X2П and the excited states a4П and B2П of NO molecule are calculated using the CASSCF/MRCI method and the cc-pVDZ basis set. The potential energy curves are obtained by a least square fitting to the modified Murrell-Sorbie function. Employing the Rydberg-Klein-Rees method, the harmonic frequency and other spectroscopic data (αe 、ωe、 ωeχe、 βe ) of the ground state X2П and the excited states a4П and B2П of NO molecule are calculated and the calculation results are in better agreement with the experimental ones than other theoretical data. In addition, the eigenvalues of vibrational levels are calculated by solving the radial one-dimensional Schrdinger equation based on the analytical potential energy function.