Abstract: A series of Cu-ZSM-5 catalysts were synthesized by hydrothermal synthesis method using silica sol as silica source and sodium aluminate as aluminum source under different synthesis conditions. The simulated flue gas was used to exams the catalyst activity for NO direct decomposition, de-NOx conditions as well as the activity stability. The results find that the best catalyst performance is achieved at the synthesis conditions of silica/alumina ratio of 60, silicon/copper ratio of 17 and pH of 10-12. The catalyst prepared shows the best thermal tolerance and feed flexibility. The optimum working conditions for de-NOx of simulated flue gas with 580 ~ 680 μg /g of NO are: gas space velocity of 18 000 h-1 with O2 volume fraction of 5% and reaction temperature of 325~425℃.Under the above conditions, the removal rate of NO reaches more than 50% and the highest removal rate can reach 61% within 40h operation. The activity stability of the catalyst is the best at 375 ℃.