Cu-SSZ-13 catalyst, as the most popular selective catalytic reduction on filter (SCRF) catalyst in diesel exhaust purification, may suffer from severe alkali deposition derived from engine oil, urea solution and biodiesel fuel. These accumulated deposits inevitably affect both of the NOx reduction and soot oxidation reactions. Unlike deactivation effect of alkali impurities on Cu-SSZ-13 catalyst for NH3-SCR process, which has been extensively studied and well documented, the impact of alkali deposition on soot oxidation over SCRF catalyst is still poorly understood. Herein, we reported the influence of potassium salts deposition on soot oxidation of Cu-SSZ-13 catalyst. Compared with the fresh Cu-SSZ-13, these K-impregnated catalysts show promoted activities toward soot oxidation with the promotion effect of K2SO4 > K2CO3 > K3PO4. The generated copper compounds instead of potassium salts are found to be responsible for the enhanced catalytic activity. The NO oxidation over the K2CO3-impregnated catalyst is accelerated by CuOx clusters, resulting in a low ignition temperature toward soot oxidation in the presence of NOx. Contrarily, K2SO4- and K3PO4-impregnated catalysts show higher ignition temperature values because the generated copper sulfates and phosphates present weakened NO oxidation activities especially in the low-temperature region. This work provides new insight into understanding the affecting mechanism of alkali impurities on SCRF catalysts. The generated Cu species induced by the deposition of different potassium salts, rather than alkali species themselves, are responsible for the promoted soot oxidation activity of the K-impregnated Cu-SSZ-13 as a SCRF catalyst.