Abstract: A pot experiment was carried out to study the effects of application of Mg on growth, biomass, nutrient content and total saponins content in different parts of Paris polyphylla var.yunnanenis. There were four levels of Mg application, namely Mg 0, 40, 80 and 160 mg/kg. The result shows that height of the plant is decreased significantly with the application of Mg. Total biomass is the highest under the Mg 80 mg/kg treatment, while the increased percentage of tube weight is under the Mg 40 mg/kg treatment. When the applied Mg is larger than these levels, the total biomass and the increased percentage of tube weight are significantly decreased. Low level of Mg (40 mg/kg) could increase K and P contents of the different parts; however, the Mg application has little effects on N content of the different parts. The Mg content in the different parts increase with the Mg application levels. The total saponins content of new tuber is highest at the Mg 80 mg/kg level, and that of old tuber is highest at the Mg 40 mg/kg level. Comprehensively considering growth, tube weight and total saponins content, the Mg 40mg/kg application is suggested for Paris polyphylla var. yunnanenis.