Panax notoginseng (Araliaceae) is an important ginseng herb with various health benefits and a history of cultivation in southwestern China over 400 years. In recent years P. notoginseng has faced serious continuous-cropping obstacles due to its large-scale cultivation. In this study, we aim to explore the allelochemicals of P. notoginseng and their interactions with various plants and rhizosphere microor-ganisms. The chemical constituents of the soil cultivated with 3-year-old P. notoginseng were studied by column chromatography, spectroscopic and GC-MS analyses. We identified 13 volatile components and isolated six triterpenes (1-4, 6-7) and one anthraquinone (5). Compounds 1-7 were tested for their effects on seed germination and root elongation in P. notoginseng, corn, wheat, turnip, water spinach and Arabidopsis thaliana. We also examined the effect of compounds 1-7 on the growth of ten rhizosphere microorganisms of P. notoginseng. At a concentration of 1.0μg mL-1, compounds 3 and 5-7 caused the death of P. notoginseng root cells and compounds 2, 6 and 7 induced the death of root cells of A. thaliana. Compounds 1-5 and 7 inhibited elongation of A. thaliana root tip cells at a concentration of 10.0μg mL-1. Moreover, at a concentration of 0.1 mg mL-1, compounds 3, 4, 6 and 7 inhibited the growth of probiotics and promoted the growth of pathogens of P. notoginseng. These results suggest that these isolated ursane-type triterpenoid acids and anthraquinone are potential allelochemicals that contribute to continuous-cropping obstacles of P. notoginseng.