Abstract: In order to improve the remediation efficiency of farmland soil with low mercury pollution，the current study was carried out to investigate the addition of chelating ligands sodium thiosulphate and fulvic acid (0.075, 0.15, 0.225 kg/m2) on mercury accumulation by Brassica juncea and mercury content transformation in soil under field condition.The biomass and the mercury content in plants and total mercury content and bioavailable mercury content in soil were analyzed after experiment．The results indicated that the dry biomass of sodium thiosulphate (0.075~0.225 kg/m2) treated plant was closed to that of the control plant．Sodium thiosulphate could enhance B. juncea uptake of mercury from soil, and transport mercury from soil to aboveground plant biomass. The dry biomass of fulvic acid treated plant was higher than that of the control plant．Fulvic acid (0.075~0.15 kg/m2) could enhance B. juncea uptake of mercury from soil, and transport mercury from soil to aboveground plant biomass also. After 0.15 kg/m2 sodium thiosulphate and fulvic acid treated, the total mercury content in the soil all decreased from 0.45 mg/kg to 0.35 mg/kg, and the bioavailable concentration of mercury in the soil decreased from 1.45 μg/kg to 0.57, 0.63 μg/kg, respectivly. The application of chelating ligands sodium thiosulfate or fulvic acid may be a potential remediation technology to promote the remediation of low mercury contaminated farmland soil by B. juncea.