An experimental study on NO removal via UV/H2O2 process was conducted in a semi-continuous bubble-column reactor and the effect of some operation parameters including NO initial concentration and gas flow rates on removal efficiency was investigated. Applying UV light increased the efficiency significantly. The steady-state removal efficiency was found to be higher at the lower gas flow rates. The bubble size as an important factor in mass transfer calculations and modeling procedure was determined at different gas flow rates using bubble photographs and image processing technique. In the ranges of flow rates studied here, the gas flow rate had no significant effect on the bubble diameter. A mathematical model was developed to describe the NO removal process. The model predictions were compared with existing experimental data, confirming a good agreement of the data.