Cu/SSZ-13 has considered being a good candidate for NH3-SCR catalysts. However, in real world, Cu/SSZ-13 inevitably expose to alkali metals deposit and hydrothermal aging, and hence, the role of alkali ions (Na+ and K+) poisoning on the hydrothermal stability of Cu/SSZ-13 was investigated in this work. The Cu/SSZ-13 catalyst was treated with different loadings of alkali content at 600 degrees C or different hydrothermal temperatures at low alkali metal loading. Different from non-poisoned Cu/SSZ-13 catalysts under hydrothermal aging, the introduced alkali ions weaken the hydrothermal stability of Cu/SSZ-13 and make poisoned catalysts have inferior SCR performance. H-2-TPR results demonstrate the presence of alkali ions lead to more copper ions transform to copper oxides species and the extents of transformation increase as the alkali contents and aging temperature increasing. Moreover, XRD results prove that the CHA framework collapse and, simultaneously, SiO2 and CuAlOx species form under high contents of alkali ions or high aging temperature. Besides, potassium invariably shows the severe deactivation because of a small hydrated diameter and strong binding ability. Our study reveals that diesel should pay attention to control the contents of alkali ions, especially for K+ in automotive products and the operating temperature in after-treatment applications.