The objective of study was to investigate effect of silicon on arsenic uptake by rice seedlings in two soils with different arsenic concentrations. The results show that the addition of silicon has little effect on shoot and root dry weights of rice seedlings. The addition of silicon did not affect shoot and root P concentrations of rice seedlings grown in low arsenic soil, but significantly increased shoot P concentrations on rice grown in high arsenic soil. Irrespective of the initial pH of K2SiO3 solution, the addition of silicon significantly decreased shoot and root As concentrations of rice seedlings compared with the control. For seedlings grown in low As-contaminated soil, As concentrations in shoot and root were reduced by 36%-59% and 15%-37% with the application of silicon, respectively. For seedlings grown in high As-contaminated soil, As concentrations in shoot and root were reduced by 42%-58% and 70%-82% with the application of silicon, respectively. These results are in agreement with our previous reports based on a solution culture experiment. Possible mechanisms of the effect of Si on As uptake was also discussed.