Abstract: Leaves of Pistacia chinensis at various developmental stages were collected and used as experimental materials to investigate the correlation between telomere length and tree age. Telomere length was quantified using quantitative polymerase chain reaction (qPCR), and the results revealed a positive correlation between telomere length and tree age in P. chinensis leaves. Based on these findings, a mathematical model was developed to describe the relationship between telomere length and tree age: L(x) = −4 × 10⁻¹¹ x² + 2 × 10⁻⁴ x + 16.707 (R² = 0.9528), where x represents telomere length and L(x) denotes tree age. Additionally, eight restriction endonucleases—Hinf I, Taq I, BamH I, BstX I, Xho I, Sal I, Hind III, and EcoR I—were evaluated to identify suitable enzymes for telomere length analysis. Terminal restriction fragment (TRF) analysis was employed to measure telomere length, and data were processed and analyzed using MATLAB software. The results indicated that Taq Ⅰ and Hinf Ⅰ effectively digested genomic DNA extracted from P. chinensis leaves. Both enzymes confirmed a gradual increase in telomere length with increasing tree age, consistent with the qPCR results, with Hinf Ⅰ demonstrating higher detection accuracy.