Silicon (Si) could decrease the uptake and accumulation of arsenic (As) in rice. We also hypothesize that silicic acid can compete strongly the co-transporters with As(III), resulting in the decrease of As(III) uptake at higher Si/As ratio, and Si/As ratio may not influence As(V) uptake significantly for both silicic acid and arsenate not sharing the same transport system in rice. However, the different Si/As ratios (0:1, 1:1, 10:1, 100:1) in nutrient solution for 24 h did not impact As (III) uptake by rice roots, whereas inhibited the translocation of As(III) from root to shoot significantly (P<0.001). Si/As at 100:1 significantly decreased As (V) uptake and As (III) efflux. Why dose Si/As not influence As(III) uptake by rice? So, A hydroponic experiment was carried out to explore the effects of Si/As ratios (0:1,100:1 and 200:1) on the uptake, efflux, translocation and accumulation of arsenic in rice seedlings that were grown in nutrient solution containing 10 µmol·L^-1 arsenite or arsenate for 12 h, 24 h and 48 h. The results showed that Si/As of 200:1 reduced arsenite uptake rate by 30.7% (P<0.05), compared with the control when rice was exposed to nutrient solution with arsenite and silicon for 12 h. The uptake rates of arsenite of rice gradually decreased and the effect of different Si/As ratios reduced with the prolongation of exposure time. Furthermore, the ratios of Si/As at 100:1 and 200:1 inhibited the translocation of arsenite from roots to shoot and the concentrations of As(III) were decreased by 51.2% and 56.9%, respectively when rice seedlings exposed to nutrient solution with arsenite for 48 h, at the same time, the concentrations of As(III) in rice shoots were significantly lower than the control, accounting for 50.7% and 67.2%.When rice seedlings were exposed to arsenate nutrient solution for 12 h, Si/As of 100:1 promoted the uptake rate of arsenate by rice, which was 82.3% higher than the control. However, the ratio of Si/As of 200:1 inhibited the uptake rates of arsenate, arsenite efflux by rice roots and translocation of As(III) after 24 h for exposure to asenate, accounting for 28.0%, 41.9% and 39.9 %, respectively. In addition, the concentrations of As(III) in rice shoots in the treatment of Si/As ratio at 100:1 and 200:1 for 24 h or 48 h were significantly lower than the control, accounting for 53.6% and 75.0%, 25.0% and 52.8%. In summary, when rice seedlings were exposed in nutrient solution with As(III) or As(V) for 12 h~48 h, the ratio of Si/As at 200:1 significantly inhibited arsenic uptake, As(III) efflux and translocation of As(III) from root to shoot.