Abstract: Anxi Tieguanyin tea, as a Globally Important Agricultural Heritage System (GIAHS), requires the synergistic improvement of both yield and quality for the 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 research focused on analyzing the interaction effects between canopy structure and environmental factors under the regulation of different cultivation models with different treatment years (particularly tea tree 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 (A1 and A2) with consistent site conditions were selected in Juyuan Village, Longjuan Township, Anxi County, Fujian Province, China (25°03′N, 118°11′E), for a comparative experiment: one using the conventional dwarfing and high-density planting (A1) and the other one adopting the “single-stem cultivation, whole-plant canopy nurturing” model (A2). To clarify the temporal effects of the two cultivation models, 3–4 years after the start of the experiment (2019−2020) (Y1-Y2) were defined as the “early experimental stage” and the 5–8 years (2021−2024) (Y3-Y6) as the “late experimental stage”. The results showed as below. 1) Dynamic yield changes: in the early experimental stage, the A1 tea garden had higher new shoot emergence density than the A2 tea garden, and the 100-tea bud weight and fresh leaf yield were also higher in the A1 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), indicating better freshness and mellowness in the tea infusion. In sensory evaluation, the average score of the tea samples from A2 tea garden in 2024 (91.88) was significantly higher than that from A1 tea garden (87.75) (P<0.05), with particularly significant improvements in aroma and taste. The “single-stem cultivation, whole-plant canopy nurturing” model initially yielded a lower fresh leaf yield, however, it synergistically enhanced 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 (a GIAHS site).