Abstract: OBJECTIVE To investigate the laws how light intensities affect the physiological characteristics, alkaloid contents and biomass of Fritillaria thunbergii Miq. METHODS With plastic net shading, four types of light intensities were set, including the light transmittance of 100%(control group CK), 50%(group T1), 25%(group T2) and 5%(group T3). Then photosynthesis parameters, alkaloid content and biomass in different shading treatments were detected separately. RESULTS Shading significantly impacted the photosynthesis, alkaloid contents and biomass of Fritillaria thunbergii Miq. Moderate shading accelerated net photosynthesis. The yield of Fritillaria thunbergii Miq. was reduced at the light transmittance of 5%, but the content of alkaloids was significantly increase. CONCLUSION The 75% shading condition helps to quicken the net photosynthesis of Fritillaria thunbergii Miq. and was beneficial to its photosynthesis, while the 95% shading condition seriously inhibites the biomass accumulation. The degree of shading is not sampletely parallel to the alkaloid.