It is an essentially ecological problem that Eupatorium adenophorum invades the karst ecosystem, which reduces community diversity and stability. Arbuscular mycorrhizae (AM) plays an important role in regulating different plant species on the soil nutrient competition. However, it is less clear how AM fungus regulates the allocation between aboveground and belowground resources of invasive and native species via root external mycelia in karst habitat. An experiment was conducted in a microcosm composed of two planting compartments and a competition compartment. The invasive plant E. adenophorum and native plant Artemisia annua were each placed in one of the two planting compartments. The experiment contained the AM fungus treatments, with AM fungus (M⁺) and without AM fungus (M^-), and the nutrient utilization treatments using nylon mesh to interconnective mycorrhizal networks, including common competition (CC), single utilization (SU) and control (CK). Biomass, nitrogen (N) and phosphorus (P) acquisition of the two species were analyzed. The results showed as follows. For aboveground parts of both invasive and native plant species, a significantly M⁺ > M^- effect was observed in P acquisition of E. adenophorum under CC, SU and CK treatments, while no significant differences were observed for A. annua. Under M⁺, the N acquisition of E. adenophorum and the biomass, N and P acquisition of A. annua were presented as SU>CK, and the biomass, N and P acquisition of A. annua were showed as CCE. adenophorum was significantly higher than that of A. annua. Under M^-, the P acquisition of A. annua was showed significantly as CC, SU>CK, but did not for E. adenophorum. For belowground parts of both species, a significantly M⁺ > M^- effect was observed in biomass, N and P acquisition of E. adenophorum under CC, SU and CK treatments, but did not for A. annua; the N acquisition of E. adenophorum had no significant differences between CC and SU, but the N acquisition of E. adenophorum was showed as SU>CK. Under M⁺, the N and P acquisition of E. adenophorum under CC and SU treatments were significantly higher than those of A. annua. Under M^-, there was no significant difference between E. adenophorum and A. annua. In conclusion, the AM fungus regulates the competition ability of invasive species with native species through the mycorrhizal network, affects the resource allocation between aboveground and belowground of plant, and improves the benefit of invasive plants from mycorrhizal symbiosis thereby promoting their invasion.