The exotic species Spartina altiflora (S.altiflora) seriously threatens the stability and functioning of saltmarsh ecosystems in the Yangtze Estuary.Ambitious efforts have been undertaken to control this species,but subsequent re-invasion is frequent,presenting a significant barrier to restoration.The complexity and high cost of integrated physical control programs has necessitated a shift in focus,leading to considerable attention being paid to the potential of herbicides to control S.altiflora.To find a strategy for emergency control of small and scattered patches of re-invading S.altiflora,an in situ field experiment using Gallant (Haloxyfop-R-methyl) herbicide was conducted.The growth parameters of plant density and height were used to evaluate the control efficiency of different treatment dosages and times and sediment samples were taken for environmental toxicity analysis.The results show the following:(1) the control efficacy of the maximum proposed application dose (2.70 g/m2) was 92％ for continuous swards and 100％ for small patches,while those of other dosages (0.45 g/m2,0.90 g/m2,and 1.35 g/m2) were lower than 40％;(2) the appropriate implementation time was July to August with 100％ mortality resulting from a single application,while S.altiflora was shown to be capable of recovering rapidly after treatment in May;and (3) there were no significant differences in the community structure of meiofauna among the herbicide treatments and the control,and no herbicide residues were detected in sediment samples collected from treatment areas.This chemical control method was implemented in the Shanghai Chongming Dongtan National Bird Nature Reserve (CDNR).The results of this study indicate that Gallant is an environmentally friendly herbicide with high efficiency,which can be adopted for emergency control of re-invading S.altiflora.