Abstract: The successful invasion of alien plants is regulated by both abiotic factors (such as changes in aboveground and underground resources) and biological factors (such as mutualistic symbionts). In this study, the typical invasive plant Trifolium repens L. was used to investigate the effects of light, phosphorus, symbiotic arbuscular mycorrhizal fungi (AMF), and their interactions on growth using a three-factor two-level orthogonal experiment. Results showed that: (1) High light, high phosphorus, and AMF inoculation significantlyincreased the biomass and growth rate of T. repens. The promotion effect of AMF inoculation on biomass increased with increasing light, and the promotion effect of AMF on total biomass and relative growth rate was more pronounced under low phosphorus conditions; (2) High light intensity reduced specific leaf area but improved the performance of other aboveground traits, except for root mass fraction. High phosphorus and AMF inoculation significantly increased the number of leaves and total leaf area, which was more obvious under high light intensity; (3) High light intensity significantly increased root surface area, root diameter, and root mass fraction, but decreased the proportion of fine roots and specific root length. The promotion effect of high light intensity on root surface area was higher under low phosphorus. High phosphorus significantly reduced the root mass fraction. In the absence of AMF inoculation, high phosphorus increased the root surface area and root diameter and decreased the proportion of fine root length. However, after inoculation with AMF, high phosphorus reduced the root surface area and root diameter and also increased the proportion of fine root length. AMF significantly reduced the root mass fraction and specific root length. Overall, these results showed that light, phosphorus, and AMF significantly affected T. repens growth, and the intensity of the effects of phosphorus and AMF on growth and aboveground traits was dependent on light intensity, while the intensity of the effects of AMF on underground traits was dependent on phosphorus concentration.