Abstract: We studied the protective effect and mechanism of isorhamnetin (ISO) on 1-methyl-4-phenylpyridiniumion (MPP⁺)-induced SH-SY5Y cells injury. MPP⁺-induced SH-SY5Y cell injury model was established, and cell viability was measured by MTT and LDH methods. The activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in cells were determined to investigate the level of oxidative stress. DCFH-DA and MitoSOX fluorescence probes were used to detect the levels of intracellular reactive oxygen species (ROS) and mitochondria superoxide, respectively. JC-1 fluorescence probe was used to detect the changes of mitochondrial membrane potential. Western blot and immunofluorescence methods were used to determine the expressions of Sirt1 and PGC-1 proteins, as well as the expression levels of apoptosis-related proteins Bax and Bcl-2. MPP⁺ at the dose of 500 μmol·L^-1 significantly reduced SH-SY5Y cells viability to 52.46% and increased LDH release to 417.63%. ISO at 5 and 15 μmol·L^-1 significantly increased the expression of Sirt1 and PGC-1α, inhibited LDH release, reduced intracellular ROS and mitochondria superoxide, inhibited the decline of mitochondrial membrane potential and increased cell viability to 61.61% and 67.55%. In addition, ISO could downregulate the expression of Bax and upregulate the expression of Bcl-2 to reduce cell apoptosis. ISO-mediated inhibition of apoptosis could be reversed by Sirt1 specific inhibitor Sirtinol. Through activating Sirt1/PGC-1α signaling pathway, ISO could reduce oxidative stress injury and inhibit cell apoptosis to protect cells from MPP⁺ injury.