Abstract: Changing farmlands to tea plantation is an important measure in response to the Grain for Green Project in the hilly region of western Sichuan Province, China. The distribution characteristics of humus fractions in soil aggregates of tea garden were studied in order to reflect the influence of tea plantation on soil quality, and to provide theoretical basis for the sustainable utilization of tea garden soil. Soil samples were collected from an abandoned land (CK) and four tea plantations with different ages (18, 25, 33, 55 years old), and examined for the distribution of humus fractions (FA, HA) in soil aggregates. The results showed that:(1) The fulvic acid (FA) content varied from 2.97 g/kg to 6.26 g/kg, while the humic acid (HA) content varied from 1.24 g/kg to 4.89 g/kg. The contents of fulvic acid and humic acid first increased and then decreased with increasing age of tea plantation, and reached to peak point with tea plantation age of 25 years. (2) With decrease in size of the soil aggregates, fulvic acid content decreased gradually, while humic acid content was higher in aggregate size of ≥ 5 mm than others. (3) The ratio of HA to FA varied from 0.30 to 0.88. ≥ 5 and < 0.25 mm aggregates showed a higher humification degree. The increase of large aggregates was beneficial to the improvement of organic matter content and quality in soils with tea plantation for 25 years. (4) The result of stepwise regression analysis showed that soil organic carbon fractions in ≥ 5, 2-5 and < 0.25 mm aggregates influenced the stability of soil aggregates. The findings suggested that tea plantation was beneficial for accumulation of humus in soil aggregates, for enhancement of humification and to increase the soil organic carbon stability. The soil carbon sink effect was strongest in the tea plantation for 25 years. After long-term tea planting (33 a), the humus content and soil C sequestration capacity decreased. So the soil structure and fertility of tea garden could be maintained by improving the management of fertilization for sustainable utilization of tea garden soils.