Selective catalytic reduction of NOx by ammonia under the exposure of alkaline and heavy metals in fly ash still remains a major challenge for NOx elimination among air pollution control. Herein, self-protective NOx reduction catalysts with remarkable alkaline and heavy metal resistance are originally designed by Ce and Cu dual active metal cations coexchanging attapulgite clays. It is revealed that the inherent Si-OH sites among attapulgite and partially exchanged Cu species effectively captured alkaline and heavy metal cation poisons through coordinate bonding or ion exchanging to protect the active components from being deactivated. Ultimately, highly efficient NOx reduction for stationary source flue gas catalytic purification is realized via the ingenious design of dual metal exchanged clay catalysts that own self-protective capacity to resist alkaline and heavy metal poisoning. This strategy paves the way for the development of low-temperature and high-efficiency denitrification catalysts with alkaline and heavy metal resistance for stationary source flue gas purification.