Ca²⁺ plays critical roles in the development of diseases, whereas existing various Ca regulation methods have been greatly restricted in their clinical applications due to their high toxicity and inefficiency. To solve this issue, with the help of Ca overexpressed tumor drug resistance model, the phytic acid (PA)-modified CeO₂ nano-inhibitors have been rationally designed as an unprecedentedly safe and efficient Ca²⁺ inhibitor to successfully reverse tumor drug resistance through Ca²⁺ negative regulation strategy. Using doxorubicin (Dox) as a model chemotherapeutic drug, the Ca²⁺ nano-inhibitors efficiently deprived intracellular excessive free Ca²⁺, suppressed P-glycoprotein (P-gp) expression and significantly enhanced intracellular drug accumulation in Dox-resistant tumor cells. This Ca²⁺ negative regulation strategy improved the intratumoral Dox concentration by a factor of 12.4 and nearly eradicated tumors without obvious adverse effects. Besides, nanocerias as pH-regulated nanozyme greatly alleviated the adverse effects of chemotherapeutic drug on normal cells/organs and substantially improved survivals of mice. We anticipate that this safe and effective Ca²⁺ negative regulation strategy has potentials to conquer the pitfalls of traditional Ca inhibitors, improve therapeutic efficacy of common chemotherapeutic drugs and serves as a facile and effective treatment platform of other Ca²⁺ associated diseases.