Abstract：In an arsenic-contaminated site of Hubei Province， the bioavailability of arsenic under different concentration and depth gradients was investigated in fluvo-aquic soil through IVG （In Vitro Gastrointestinal） and UBM （Unified BARGE Method） in vitro. The results showed that the bioaccessibility of arsenic in the gastric fluid and duodenal fluid were 4.50%~26.41% and 3.95%~22.39%， respectively. Pearson correlation and principal component analysis were used to explore the possible sources of absorbable arsenic in the human gastrointestinal. The results showed that arsenic easily absorbed in the human gastrointestinal correlates significantly with the fractions of nonspecifically sorbed， specifically sorbed， and poorly crystalline Fe oxide-bound. Based on a multiple linear regression analysis， it was found that soil pH， total arsenic concentration， and sand concentration were the main predictors of bioaccessible arsenic concentration. Comparing the upper limit of arsenic background concentration from the probability accumulation analysis with the background values of arsenic in Hubei Province soil and fluvo-aquic soil （appendixA. GB36600）， it was derived that the upper limit of the soil arsenic background concentration was 113 mg?kg-1 in terms of bioavailability. For planning ecological preservation green space， these results could provide references for setting remediation targets and help avoid the high costs due to high remediation requirements.