Temporal changes of the total iron, free iron, chelated iron,amorphous iron,free degree,complex(chelating) degree and activation degree of soil iron oxides in the topsoil of the paddies after reclamation in the Sanjiang Plain were studied.The results showed that total iron in the topsoil of the paddies increased exponentially with time since reclamation. Free iron showed a fluctuating upward trend with the wave troughs appeared in the 3rd year and the 11th year, and the wave peaks in the 5th year and the 14th year. Chelated iron increased during the first eight years after reclamation, reached 1562.41 mg/ kg at the 8th year, and then decreased. Amorphous iron decreased exponentially with time. Free degree of soil iron oxides first increased then decreased, and reached a maximum value of 0.46 at the 8th year.Complex degree increased continuously to a maximum value of 0. 18 during the first 8 years, with a slower increasing rate from the 5th to 8th year;and decreased gradually after the eighth year. Activation degree decreased exponentially with time.Different variation trends of free degree,complex degree and activation degree of soil iron oxides between paddies and soybean fields were caused by water flooding in paddies and differences in farming methods between the two systems. Compared with the natural wetland, rice cultivation increased contents of free iron,chelated iron and amorphous iron as well as free degree of soil iron oxides, but decreased contents of complex degree and activation degree of soil iron oxides. However, complex degree and activation degree of soil iron oxides in paddies were greater than those in soybean cultivation stage.