The absorption of NO on the Pt (111) surface is investigated based on the density functional theory and the periodic slab model. The absorption structure is analyzed through scanning tunneling microscopy (STM) image. The calculated Pt-NO stretching vibration (2) frequency is almost unchanged, and the frequencies of blocked translation (3, 4) and blocked rotation (5, 6) are completely degenerate. The dissociation processes of NO on Pt (111) surface are discussed in detail using the CI-NEB method. The results show that the dissociation of NO on Pt (111) surface is difficult and it must overcome 2.29 eV energy barrier to achieve it.