Abstract: In order to solve the problem of uneven ammonia injection in depth direction of vortex mixer denitrification system, double row eddy mixing device had been reformed in a power plant. By comParing the NO_x concentration distribution and ammonia escape in SCR outlet before and after the transformation, it was verified that the structure of double row eddy vortex disc is superior to that of single row vortex disc in the uniformity of ammonia injection. The NO_x concentration nonuniformity of A side was 8.2% while the B side was 5.4% in denitrification inlet before reformation. The dietribution of NO_x concentration in denitrification inlet was uniform. The nonuniformity of the A flow field was 23%, while the B flow field was 24.9%. The flue gas flow field was relatively uniform. The nonuniformity of NO_x concentration in A side denitrification outletwas 64.1% while the B side was 63% before reformation. Ammonia escape concentration in denitrification outlet was more than 3 μL/L before reformation. The uneven distribution of NO_x concentration in denitrification outlet, was mainly caused by the structure of single row vortex mixer which lead to the uneven ammonia injection. Due to the single row vortex mixer transformed into a double row vortex mixer, the NO_x concentration nonuniformity in A side of the denitrification outlet decreased to 35.8% while the B side decreased to 37%. After the reformation, the average escape concentration of ammonia in denitrification outlet was generally less than 1 μL/L. The parameters showed that the double row eddy vortex disc can reduce the unevenness of ammonia injection, the effect on the uneven distribution of NO_x concentration along the flue depth was remarkable especially. For the single row eddy vortex disc denitrification system with large ammonia escape caused by uneven ammonia injection, the double eddy vortex disc transformation could be considered. The experimental study provided a idea and guidance for the denitrification transformation.