Abstract: To investigate the adaptation strategies of 1-year-old Fraxinus mandshurica and Phellodendron amurense seedlings under low light and to determine their optimal growth light intensities, four light intensity treatments（100%, 75%, 45%, and 15% full light, noted as L100, L75, L45, and L15） were used to observe the growth, photosynthetic characteristics and non-structural carbon（NSC） content of 1-year-old seedlings of both species and their allocation. The results showed that the growth indexes（photosynthetic tissue to non-photosynthetic tissue biomass ratio showed an opposite trend）, basic photosynthetic parameters and photosynthetic product indexes of the Fraxinus mandshurica seedlings, except for the ground diameter, were highest under L45 treatment, and some of them were significantly different（P＜0.05） compared with those under L15 and L100 treatments. The growth indexes, basic photosynthetic parameters and photosynthetic product indexes of the Phellodendron amurense seedlings were highest under L100 light intensity, and the differences were significant（P＜0.05） compared with the other three light intensities. The chlorophyll（Chl） indexes of both species decreased with increasing light intensity（Chl a/b increased）. In addition, the plasticity of each index of both seedlings was greater in Phellodendron amurense than in Fraxinus mandshurica, and the top three plasticity values of Fraxinus mandshurica seedlings were, in descending order, seedling quality index, root biomass, and Chlb, while those of Phellodendron amurense seedlings were, in descending order, seedling quality index, leaf biomass, and root biomass. In conclusion, 1-year-old Fraxinus mandshurica seedlings were highly shade tolerant with an optimum growth light intensity of 45% full light（L45）; 1-year-old Phellodendron amurense seedlings were less shade tolerant with an optimum growth light intensity of 100% full light（L100） and may die with increasing shade time.