Dielectric barrier discharge was used to study the NO molecules of the atmosphere pollution, and the fluorescence emission spectrum in the range of 210-280 nm at low pressure was obtained in this plasma. The spectrum shows obviously the structure of double apices, whose intensity distribution in accord with Frank-Condon principle and the maximum lies at 236 nm. The main lines are attributed to the A 2 sigma+ -->X 2 pi 1/2, 2/3 transition. The produce of fluorescence can be described as: NO molecules at the ground state are impacted to the A 2 sigma+ excited state by fast electrons, and then transit to the ground state radiating fluorescence. By measuring the relation between discharge time and emission intensity of NO and N2 molecules in the discharge plasma, we demonstrated the dissociation mechanism of NO in the discharge period, which can be interpreted as: e* + NO-->N + O + e, N + NO-->N2 + O, O + NO-->NO2 + h nu.