Eriophyoid mites are highly specific to host plants. In this study we identified a new species (Phyllocoptes maackissp. nov.) from Euonymus maackii Rupr. (Celastraceae) and explored its population dynamics and relationship with abiotic factors (i.e., temperature and rainfall). We determined that P. maackissp. nov. is vagrant on lower leaf surface and does not damage the host plant. Additionally, it was first detected in June. Its population peaked in July and decreased in August. The mites were undetectable on leaves in September. Thus, P. maackissp. nov. was active in the summer when conditions were suitable (e.g., most of the leaves were young and full of moisture), with peak activity in July under high-temperature conditions. Its activity decreased under suboptimal conditions, such as low temperatures and heavy rainfall. The abundance of eriophyoid mites varied over time. The increase and decrease in the number of eriophyoid mites during the study period was basically consistent with the temperature changes.