Eupatorium adenophorum is the most damaging invasive alien species in China and unbalances local ecosystems and threatens the survival of native species,thus,attracting increasing attention from all sectors of society.Exploring interspecific associations of E.adenophorum and the stability of companion species after invasion is an important starting point for studying the interaction of invasive and native species.To effectively predict and evaluate the level of E.adenophorum invasion,we investigated invaded areas in Liangshan Prefecture of Sichuan,using 2×2 contingency table analysis and χ² and W tests to analyze interspecific associations,using the association coefficient (AC),percentage of co-occurrence (PC),Ochiai index (OI),Dice index (DI),Godron M method,of Xichang City and Huili,Huidong,Dechang,and Puge counties.There were 155 companion plant species in the E.adenophorum community in Liangshan Prefecture,including 86 herbaceous plants,34 shrubs,22 trees,10 vines,2 ferns,and 1 bryophyte.The χ² and W tests results indicated that the variance ratio of overall association of major plants in the E.adenophorum community was 0.9677 < 1,χ_0.95²(50)< W < χ_0.05²(50),which indicates a non-significant negative correlation among the main species.The χ² values among the various species were all lower than 3.841,indicating that the two main species were only slightly associated or even independent.Dominant species in the E.adenophorum community were similarly or equally adapted to the environment,and competition existed in the utilization of natural resources.Interspecific association analysis indicated that 20 pairs of species were positively correlated and that 22 pairs exhibited negative correlations or were completely independent.The percentages of co-occurrence of E.adenophorum with Bidens pilosa,Artemisia lavandulaefolia,Digitaria sanguinalis,and Physalis peruvianal ranged from 0.4 to 0.6,and the OI and DI indices were all over 0.6,which indicated that E.adenophorum had similar or identical ecological needs and adaptability to the environment,but also that B.pilosa,A.lavandulaefolia,D.sanguinalis,and P.peruvianal had strong resistance to the inhibitory properties of E.adenophorum.Community stability analysis indicated that the intersection point of the model equation and linear equation was 51/49,which was far from the stable intersection point 20/80,thus indicating that the E.adenophorum community was unstable.Therefore,we concluded that local plant communities in southwest China become relatively unstable after being invaded by E.adenophorum,interspecific segregation will occur to lower the competition intensity among the various species,thus the plant communities tends to be stable gradually.This conclusion could be referenced for predicting and evaluating the degree of invasion by E.adenophorum as soon as possible.