Abstract: A pot experiment was conducted to investigate the effects of silicon (Si) supply on diurnal variations of photosynthesis and transpirationrelated physiological parameters at rice heading stage under elevated UV-B radiation. The experiment was designed with two UV-B radiation levels, i.e. ambient UV-B (ambient, A) and elevated UV-B (elevated by 20%, E), and four Si supply levels, i.e. Si₀ (control, 0 kg SiO₂·hm^-2), Si₁ (sodium silicate, 100 kg SiO₂·hm^-2), Si₂ (sodium silicate, 200 kg SiO₂·hm^-2), Si₃ (slag fertilizer, 200 kg SiO₂·hm^-2). The results showed that, compared with ambient UV-B radiation, elevated UV-B radiation decreased the net photosynthesis rate (P_n), intercellular CO₂ concentration (C_i), transpiration rate (T_r), stomatal conductivity (g_s) and water use efficiency (WUE) by 11.3%, 5.5%, 10.4%, 20.3% and 6.3%, respectively, in the treatment without Si supply (Si₀ level), and decreased the above parameters by 3.8%-5.5%, 0.7%-4.8%, 4.0%-8.7%, 7.4%-20.2% and 0.7%-5.9% in the treatments with Si supply (Si₁, Si₂ and Si₃ levels), respectively. Namely, elevated UV-B radiation decreased the photosynthesis and transpirationrelated physiological parameters, but silicon supply could obviously mitigate the depressive effects of elevated UV-B radiation. Under elevated UV-B radiation, compared with control (Si₀ level), silicon supply increased P_n, C_i, g_s and WUE by 16.9%-28.0%, 3.5%-14.3%, 16.8%-38.7% and 29.0%-51.2%, respectively, but decreased T_r by 1.9%-10.8% in the treatments with Si supply (Si₁, Si₂ and Si₃ levels). That is, silicon supply could mitigate the depressive effects of elevated UVB radiation through significantly increasing P_n, C_i, g_s and WUE, but decreasing T_r. However, the difference existed in ameliorating the depressive effects of elevated UV-B radiation on diurnal variations of physiological parameters among the treatments of silicon supply, with the sequence of Si₃>Si₂>Si₁>S/a#₀. This study suggested that fertilizing slag was helpful not only in recycling industrial wastes, but also in effectively mitigating the depressive effects of elevated UV-B radiation on photosynthesis and transpiration in rice production.