Abstract: The effects of all optical，30%，50%，70% and 90% shading treatments on the growth and photosynthetic characteristics of Phyllitis japonica were studied. The results showed：With the increase of light intensity，the leaf area，fresh weight of unit leaf area，chlorophyll content，and leaf water content decreased and soluble sugar and soluble protein content declined. The diurnal variation of net photosynthetic rate（Pn）presented the double-peak curve，indicating there was midday depression of photosynthesis; the optimum treatment to diurnal average Pn was 50%–70% shading. The light compensation point（LCP）reduced gradually and the light saturation point（LSP）was the highest under 50% shading，which was lower in 70% and 90% shading. Comprehensively，the suitable light environment of Phyllitis japonica was 50%–70% shading.

Key words: fern, Phyllitis japonica Kom., photosynthetic physiology, light adaptability