We reported a new one-pot method to synthesize Cu incorporated ZSM-5 with ethylene diamine tetraacetic acid copper disodium salt hydrate (EDTA-Cu) as copper source by a hydrothermal process. The obtained isomorphous substituted Cu-ZSM-5 exhibits more excellent reactivity for selective catalytic reduction of NO_x by NH₃ with long term stability than their conventional copper impregnated counterparts. The results indicate that the tetracoordinated Cu species in the ZSM-5 frameworks have superior catalytic properties than the Cu species existed outside the ZSM-5 zeolites frameworks. The novel ammonium salt complex method was used for the first time to synthesize the metal-ZSM-5 molecular sieves.