In this study, using quadratic saturation D-optimal design method, the effects of UV-B radiation on tomato seedling growth characteristics were studied with different varieties. The mathematical models between seedling growth, seedling index, and UV-B radiation intensity and radiation time were established, and the biological effects of UV-B were discussed. The results showed that UV-B radiation significantly affected the growth of tomato seedlings, and the response of different tomato varieties to UV-B radiation was consistent. The tomato plant height was decreased, and the stem diameter, crown and root dry mass and seedling index were firstly increased and then decreased with the increase of UV-B radiation intensity and time. The interactive effect between UV-B radiation intensity and time was significant. UV-B radiation intensity had a greater effect on plant height than radiation time, but it was opposite on stem diameter and seedling index. After simulation calculation, the appropriate intensity and time of UV-B radiation were 14.5-25.6 μW·cm^-2 and 4.1-5.8 h·d^-1, respectively, for cultivating highquality tomato seedlings.