Abstract: To elucidate the systemic distribution of fosetyl-aluminum in Torreya grandis and its field efficacy against root rot, HPLC-MS was employed to trace the presence of the compound across different parts of three-year-old T. grandis at 7, 14, and 21 days after trunk injection. A 0.5% SL was applied to 13-year-old T. grandis through trunk injection, once annually in mid-March, over a 3-year period. At the end of the third year, the residue levels of fosetyl-aluminum in different T. grandis tissues and changes in leaf photosynthesis activity were assessed. Seven days after the 0.5% fosetyl-aluminum SL trunk injection, the compound was systemically distributed to the roots, stems, branches, and leaves, with concentrations reaching 0.51 mg/kg in the branches and stems, and 0.15 mg/kg in the roots. The three-year application achieved a remarkable 89.41% control efficacy against root rot in T. grandis. Furthermore, the trunk injection of fosetyl-aluminum increased photosynthetic pigments, including chlorophyll, while reducing heat dissipation and carotenoid content in the leaves, thereby enhancing photosynthetic capacity. This led to normal leaf sprouting, rejuvenation, and re-greening. Collectively, fosetyl-aluminum, when applied via trunk injection, can move bi-directionally within T. grandis and is an effective treatment for root rot control.