The invention discloses an oxidation device for NOx in flue gas. The oxidation device comprises an oxidation tower and an ozone generator, wherein an oxidation medium inlet is formed in the oxidationtower, a fixed bed of the oxidation tower is provided with a physical adsorption layer, and the oxidation medium inlet is higher than the top end of the physical adsorption layer; an oxidation mediumoutlet of the ozone generator is communicated with the oxidation medium inlet of the oxidation tower, a flue gas inlet of the oxidation tower is communicated with a flue gas output pipeline, and a flue gas outlet of the oxidation tower is communicated with a chimney through a flue. The invention also discloses an oxidation process, in combination with advantages and disadvantages of physical adsorption enrichment oxidation and ozonation, physical adsorption enrichment oxidation is adopted in an area with higher Nox in flue gas at the inlet of the oxidation tower, and part of NO is oxidized into NO2 under the condition that an additional oxidizing agent and energy are not consumed; when the NO concentration is reduced to a certain degree, ozone is further adopted for deep oxidation, so thatNO which is difficult to remove by wet absorption in NOx is oxidized to NO2 easy to absorb. The oxidation device can realize high oxidation rate of NO under the condition that little ozone is consumed.