Abstract: Pyrimethanil, a phenylamino-pyrimidine fungicide, exhibits effective control against tomato gray mold (Botrytis cinerea), but its conventional formulations face challenges such as low utilization efficiency and potential environmental pollution. To improve control efficacy of pyrimethanil against tomato gray mold and achieve intelligent release, this study developed a metal-organic framework (MOF) carrier system responsive to the acidic microenvironment typically induced by fungal infections. The pyrimethanil-loaded nanoparticles (Pyr@ZIF-8) with regular morphology and good stability were successfully synthesized via a one-pot method based on zeolitic imidazolate framework-8 (ZIF-8), with a drug loading capacity of 14.72% and an average particle size of (346.80 ± 5.44) nm.The drug delivery system demonstrated significant pH-dependent release kinetics, with cumulative release rates of 84.94% and 53.60% at pH 5 and pH 9, respectively. This pH-responsive behavior, characterized by faster release under acidic conditions and slower release under alkaline conditions, was primarily driven by the framework erosion mechanism. Plate inhibition assays revealed that Pyr@ZIF-8 exhibited the lowest EC₅₀ value (6.68 mg/L) compared to free pyrimethanil (7.93 mg/L), the ZIF-8 carrier (9.66 mg/L), and the physical mixture of Pyr + ZIF-8 (7.40 mg/L). The pot experiment results showed that 14 days after application, the control efficacy of Pyr@ZIF-8 was 77.00% (protective effect) and 65.27% (curative effect), significantly higher than that of the commercial 40% pyrimethanil suspension agent (36.41% and 24.26%, respectively).This pH-responsive controlled-release system significantly enhances the biological activity of pyrimethanil through nano-carrier synergistic effects, providing a promising strategy for the precise and efficient application of pesticides.