Arbuscular mycorrhizal fungi (AMF) can protect host plants against arsenic (As) toxicity. However, knowledge on the response of woody leguminous under As stress is limited so far. In this study, Sophora viciifolia seedlings were inoculated with/without AMF Rhizophagus intraradices, and S. viciifolia were grown in three levels (0, 50, and 100 mg As kg−1 soil) of As-polluted soil though the potted experiments. The objective of this study was to investigate the influences of AMF symbiosis on woody leguminous under As stress. Some physiological and biochemical parameters of S. viciifolia, which included the plant growth, photosynthesis, oxidative damage, antioxidant enzyme activities and gene expression of phytochelatins (PCs), were analyzed. The results showed that As toxicity in soils inhibited the AM colonization rate, plant growth, photosynthesis, increased the oxidative damage and antioxidant enzyme activities, and up-regulated the gene expression of SvPCS1 in the leaves and roots of S. viciifolia seedlings. However, compared with non-inoculated S. viciifolia at the same As level, R. intraradices-inoculated S. viciifolia had higher shoot and root dry weight, plant height, root length, photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (E), maximal photochemical efficiency of PSII photochemistry (Fv/Fm), actual quantum yield (ΦPSII), and photochemical quenching values (qP), as well as lower intercellular CO2 concentration (Ci) and non-photochemical quenching values (NPQ). R. intraradices inoculation inhibited the malondialdehyde (MDA), H2O2, and O2•– concentrations, but improved the activities of antioxidative enzymes (SOD, POD, and CAT) in S. viciifolia leaves and roots. The gene expression of SvPCS1 in the leaves and roots was obviously up-regulated by R. intraradices inoculation. These results demonstrated that R. intraradices inoculation enhanced the As tolerance of S. viciifolia seedlings, owing to the beneficial effects of AMF symbiosis on improving the plant growth, gas exchange, chlorophyll fluorescence, antioxidant enzymes, reactive oxygen species and gene expression of SvPCS1 in S. viciifolia seedlings. R. intraradices is possible to get involved in the defence response of S. viciifolia seedlings against. As toxicity stress. This investigation got more profound insights into As tolerance mechanisms of woody leguminous associated with AMF symbiosis.