Abstract: Field plot experiments were conducted to study the effect of two-year consecutive As stress [As(V): 0, 20, 80, 140, 200 and 260 mg·kg^-1] on contents of As, saponin and flanovoids, the enzyme activities of phenylalanine ammonia lyase (PAL), chalcone synthase (CHS), and squalene synthase (SS) in main root, fibrous root and rhizome and shoot, and proteome of three-year old Panax notoginseng in Wenshan prefecture, Yunnan Province, China. The results showed that total saponin content of fibrous root decreased with increase in As treatment concentration. Total saponin contents of shoot and rhizome increased with 140 mg·kg^-1 As treatment compared with control. SS activity of rhizome was higher than that of shoot. Flavonoid contents of diffe-rent plant parts decreased with increase in As treatment concentration. With 140 mg·kg^-1 As treatment, activities of PAL and CHS in rhizome were higher than that in shoot. CHS activities in shoot and rhizome were lower, and PAL activities were higher than those of the control. As contents in different plant parts of P. notoginseng increased with increase in As treatment concentration. The highest As content was observed in fibrous root. With 140 mg·kg^-1 As treatment, twenty-one diffe-rential proteins (ratio >2, P<0.05) were identified in the inoculated compared to the control. The down-regulated proteins included phosphoribulokinase, heat shock protein, NAD(P)-binding rossmann-fold superfamily proteinisoform, monodehydroascorbate reductase and cytochrome b6-f complex iron-sulfur subunit. The up-regulated proteins included CDC27 family protein, acidic endochitinase isoform, symbiosis receptor-like kinase precursor, isoflavone reductase-like protein, phospho-2-dehydro-3-deoxyheptonate aldolase, putative protein kinase superfamily protein, malate dehydrogenase, glyoxalase I isoform and glutamine synthetase cytosolic isozyme. In general, with two-year consecutive As stress, As contents in different plant parts of P. notoginseng increased, which not only affected the photosynthesis and energy, but also decreased the antioxidation and resilience, and induced the increased expression of protein involved in detoxication, resulted in decrease in the contents of flavonoid and saponin. The tolerant threshold value of P. notoginseng for As was 140 mg·kg^-1.