AIM: To study the effect of exogenously administered dithiothreitol (DTT) on eye lens of adult rats exposed to ultraviolet radiation B(UV-B) from 300nm irradiation. METHODS: Thirty-two male SD rats aged 6 weeks (body weight about 180g) were randomly divided into four groups of 8 rats each. The first group, the model group, was exposed daily to ultraviolet radiation from 300nm at 1×10³μW/cm²for 15 minutes for one week. The second group, the experimental group, exposed in the same way as the first group, received 400μg DTT in 1mL saline 30 minutes prior to radiation, daily. The third group was also exposed to UV-B, and treated only with 400 μg DTT in 1mL saline for another week. The fourth group was kept as the control group and received a daily vehicle injection.  RESULTS: DTT injection with radiation significantly reduced lipid peroxidation, Ca²⁺ and LDH. When DTT was injected after radiation, SOD and GSH-px enzyme activities increased significantly. Also DTT significantly reduced the turbidity of the cortical cataract. CONCLUSION: Our data shows that DTT has obvious inhibitory action on ultraviolet cataract.