Abstract: The study on the photosynthetic characteristics of seedling Toona ciliata from different half-sib families aims to provide a theoretical basis for the selection and cultivation of Toona ciliata families. Taking Toona ciliata from 6 half- sib families of 2- year- old seedlings as test materials, the authors studied the photosynthetic characteristics among the families. The results showed that the diurnal variation of photosynthetic rate and transpiration rate presented double peak curves and had the‘midday depression’ phenomenon. The mean value of the daily average net photosynthetic rate was 3.49 μmol/(m2·s), transpiration rate was 2.44 μmol/(m2·s), water use efficiency was 1.43 μmol/(m2·s), light saturation point was 1165 μmol/(m2·s) and light compensation point was 42 μmol/(m2 ·s), CO2 saturation point was 1897 μmol/mol, CO2 compensation point was 104.5 μmol/mol. Comprehensive parameter analysis showed that Toona ciliata was an intolerant tree species, the CO2 utilization range was wide, and No. 1 family was the best among the 6 half-sib families.