Abstract: In order to understand the growth rule of the medicinal plant Thlaspi arvense under the enhanced ultraviolet（UV-B）radiation,the 2-months-old seedlings of T.arvense were taken as materials,two different radiation intensities were supplemented artificially with 3.26μW·cm^-2（T1）and 9.78μW·cm^-2（T2）on the basis of natural light,and the T.arvense grown under natural light as the control,to investigate the response of various physiological indicators and secondary metabolites to different UV-B radiation intensities,such as photosynthetic indicators and chlorophyll fluorescence parameters,photosynthetic pigments（chlorophyll a and b）content,osmotic adjustment substances（malondialdehyde,soluble protein,soluble sugar and proline）content,activity of antioxidant enzymes（SOD,POD,CAT and APX）,and the content of total flavonoids,total phenols and sinigrin.The results showed:net photosynthetic rate,stomatal conductance,transpiration rate,intercellular CO₂ concentration,maximum fluorescence（F_m）,PSⅡmaximum photochemical efficiency（F_v/F_m）and Potential Photochemical Efficiency of PSⅡat Two Radiation Intensities（F_v/F₀）and other chlorophyll fluorescence parameters decreased with the increasing of radiation intensity respectively.However,the chlorophyll a and chlorophyll b,osmotic adjustment substances,such as soluble protein,soluble sugar and proline,superoxide dismutase（SOD）,peroxidase（POD）,catalase（CAT）and ascorbate catalase（APX）,total phenols and sinigrin firstly increased and then decreased with the increase of radiation time,while the total flavonoids content gradually increased,which was significantly different（P＜0.05）from the control in the late radiation period.According to the comprehensive analysis of the research results,under different radiation intensities,T.arvense might improve the synthesis of total flavonoids and total phenols,the accumulation of soluble protein and soluble sugar,and the content of chlorophyll,and the activity of superoxide dismutase and peroxidase and catalase increased,to resist the influence of ultraviolet stress,and then showed the resistance and the adaptability to the stress environment of adversity.The results provided a theoretical basis for breeding and further utilization of T.arvense.