Abstract: An experiment was conducted to investigate the effects of ozone, drought and their interaction on pigment content and fluorescence physiology in 1-year-old Catalpa ovata seedlings. The results show that water content and relative water content of C.ovata decrease significantly under drought treatment, but no significant change under ozone treatment. Drought is the main reason for water loss of leaves under combined treatment. The content of chlorophyll and carotene in the leaves of C.ovata raise first and then decrease under ozone or drought treatment. Middle drought could slow down the degradation of photosynthetic pigments with ozone, but severe drought aggravated the damage. ΦPSII and F_v/F_m raise sharply under mild drought treatment, no significant change under the ozone treatment, but significantly reduce under severe drought treatment, interaction of ozone and severe drought have synergistic effects and significantly reduce F_v/F_m of C.ovata leaves. C.ovata has certain resistance to elevated ozone concentration and drought, mild drought could improve the photosynthesis of C.ovata, but ozone and severe drought have synergistic damage on the photosynthetic system of C.ovata.