Hypoxia-induced resistance to tumor treatment restricts further development of photodynamic therapy. Instead of simple reoxygenation to relieve hypoxia in traditional therapeutic approaches, a mitochondria-targeted reactive oxygen species (ROS) amplifier is constructed to reverse hypoxia resistance and enhance tumor sensitivity to hypoxia-resistant photodynamic therapy. Mesoporous silica nanoparticles are modified with triphenylphosphine to enhance its blood circulation and endow it with mitochondria-targeted specificity. α-Tocopherol succinate and indocyanine green are loaded in mitochondria-targeted mesoporous silica nanoparticles to reduce innate oxygen consumption by blocking mitochondrial respiration chain, leading to endogenous mitochondrial ROS burst and imaging-guided photodynamic therapy. This mitochondria-targeted oxidative stress amplifier not only disrupts mitochondrial redox homeostasis and triggers long-term high oxidative stress but also makes tumor more sensitive to hypoxia-resistant photodynamic therapy. The imaging-guided ROS amplifier confirms the feasibility and effectiveness of both in vitro and in vivo anticancer performance, suggesting a promising clinical strategy in hypoxia-related tumor treatment.