The selective hydrogenation of C≡C to C=C bonds is an important step,yet remains to be a great chal-lenge in chemical industry.In this study,we have revealed the influence of Pd deposition pH value on the catalytic performance of Pd-CuO/SiO2 catalyst for the semi-hydrogenation of 2-methyl-3-butyn-2-ol(MBY).Trace amount of Pd (about 500 ppm) was loaded via deposition-reduction method on CuO/SiO2 support by using H2PdCl4 solution as precursor and NaBH4 as reductant,respectively.The pH value at which Pd was deposited was adjusted to about 5 and 7 by adding NaOH solution.The obtained catalysts were characterized by several techniques including XRD,TEM,H2-TPR,etc.In the case of pH value of 5,the CuO was partially dissolved during the deposition and then co-reduced with Pd2+ by NaBH4,forming PdCu alloy structure in sub-nanometer.In contrast,no PdCu alloy structure was observed when pH value was 7.The kinetics of MBY semi-hydrogenation over both catalysts were compared.The former PdCu al-loy catalyst showed very high selectivity towards the semi-hydrogenation of MBY due to its low activity in hydrogenation of C=C bond in 2-methyl-3-buten-2-ol (MBE).The results herein demonstrated that the pH value where Pd was deposited played a crucial role in determining the catalytic performance of PdCu catalyst.