Different Cu precursors were adopted to adjust the isolated Cu²⁺ ions and CuO species in the Cu-SSZ-13 catalysts. The Cu²⁺ ions were mainly located at eight-member rings in the catalysts with the Cu precursors of Cu(NO₃)₂ (Fresh-I) and CuSO₄ (Fresh-II), while that located at six-member rings in the catalysts with the Cu precursors of CuCl₂ (Fresh-III) and Cu(CH₃COO)₂ (Fresh-IV). All catalysts showed>90% of NO conversion and 100% of N₂ selectivity at 200–680 °C. Fresh-I and Fresh-II catalysts showed an unexpected increase of the high-temperature activity after hydrothermal treatment. The characterizations revealed that the hydrothermal treatment promoted the production of CuO species, which accelerated the adsorption of NO_x species to enhance the high-temperature SCR activity. Moreover, the SCR reaction pathway changed from Langmuir-Hinshelwood to Eley-Rideal mechanisms for the Fresh-II catalyst after the hydrothermal treatment, which was verified by in situ DRIFTS.