Due to the restriction of chemical fertilizer in organic agricultural systems, soil degradation featured with poor soil structure and insufficient fertility is a bottleneck limiting the quality and yield improvement of organic tea plantation. Earthworms play a vital role in the regulation of soil ecosystem services. This study aimed to find an effective method for sustainable utilization of organic tea garden soil structure improvement and fertility improvement. In order to investigate the effects of earthworms on soil structure and soil carbon distribution in organic tea plantation, we inoculated Metaphire guillelmi into the soil with different densities, 375/m², 250/m², 125/m² respectively. The results showed that the earthworm inoculation affected soil aggregate size distribution. It significantly increased the proportion of large aggregates (d>2mm) and reduced the proportion of micro aggregates (d<0.25mm). The proportion of small water-stable aggregates (0.25mm≤d≤2mm) was also increased. But for large water-stable aggregates (d>2mm), Here was no significant influence. Mean weight diameter (MWD), geometric mean diameter (NWD), dimension (D), and percentage of aggregate disruption (PAD) of high-density earthworm treatment were significantly higher than those treatments of lower densities and Control (CK). ¹H nuclear magnetic resonance (NMR) relaxometry could be used to study pore size distributions in soil samples efficiently and non-destructively. The distribution of soil porosity (pore size distribution) was more important than the total porosity. To measure the distribution of soil pores, the nuclear magnetic resonance method was introduced in this study, which made up for the defect of the traditional methods that could not distinguish capillary pores. Earthworm inoculation increased the proportion of structural pores (the intergranular and interaggregate pores), among which the increase of pores between aggregates was the most significant, followed by intergranular pores. Here was no significant effect on the abundance of interlayer space between clay particles and mineral layers. With the increase of inoculation density, the relative and absolute values of porosity between aggregates increased significantly, while the difference of porosity between particles was not significant. Therefore, earthworm inoculation could improve the aeration and water permeability of soil. Earthworm inoculation could significantly increase soil respiration, soil microbial entropy, and total amount of soil active organic pool. That is, earthworm activity accelerated the renewal of soil organic carbon. The increase of inoculation density had little effect on the total amount of active organic carbon pool, but it had more effect on the soil respiration rate. Therefore, it is more appropriate to consider low inoculation density from the perspective of greenhouse gas emission. It can be concluded that a small amount of earthworm inoculation in the organic tea garden are enough to improve the soil structure and improve the soil fertility. It can also alleviate the structural problems of soil compaction caused by trampling and compaction when tea leaves are picked.