Abstract: Anxi Tieguanyin tea, as a Globally Important Agricultural Heritage System (GIAHS), requires the synergistic improvement of both yield and quality for sustainable development of the tea industry. Through long-term fixed-site monitoring, this study aimed to systematically evaluate the long-term effects of the innovative cultivation model “single-stem cultivation, whole-plant canopy nurturing” (characterized by sparse planting, single-stem fixation, whole-plant canopy nurturing, and ecological rotational plucking) on the ecosystem stability and tea quality in Anxi Tieguanyin tea gardens. Through long-term monitoring at a fixed site, this study analyzed the interaction effects between canopy structure and environmental factors under different cultivation models with different treatment years (particularly tea plant age), as well as their dynamic influence mechanisms on tea plant physiological metabolism, fresh tea leaf yield, and the accumulation of quality components. In 2016, two cultivation models conventional dwarfing and high-density planting (A1); single-stem cultivation, whole-plant canopy nurturing (A2) with consistent site conditions were selected in Juyuan Village, Longjuan Township, Anxi County, Quanzhou City, Fujian Province, China for a comparative experiment. To clarify the temporal effects of the two cultivation models, we defined 4–5 years after the start of the experiment (2019−2020) (Y1-Y2) as the early experimental stage and 6–9 years (2021−2024) (Y3-Y6) as the late experimental stage. The results are summarized as below. 1) Yield dynamics: in the early experimental stage, the A1 tea garden had higher new shoot emergence density, 100-tea bud weight, and fresh leaf yield than the A2 tea garden. However, in the late stage, A2 tea garden exhibited a significant increase in fresh leaf yield, reaching 924.68 kg∙hm⁻² in 2024, which was 13.80% higher than that of A1 tea garden (812.57 kg∙hm⁻²) (P<0.05). 2) Quality improvement: the phenol-to-amino acid ratio in A2 tea garden (11.56) was lower than that in A1 tea garden (12.57) in 2024, indicating better freshness and mellowness in the tea infusion. In sensory evaluation, the average sensory score of the tea samples from A2 tea garden in 2024 was higher than that from A1 tea garden (91.88 vs. 87.75, P<0.05), with significant improvements in appearance, soup color, aroma, taste and infused leaves. The “single-stem cultivation, whole-plant canopy nurturing” model initially exhibited a lower fresh leaf yield, while it synergistically enhanced the tea yield, quality, and garden ecological health in the long term. This ideal model provides a new paradigm integrating production, ecology, and culture for the conservation of GIAHS, offering a scientific basis for the sustainable management of Anxi Tieguanyin tea gardens.