Dissimilatory iron reduction, an important microbial process of the degradation of organic matter in anaerobic environment, is closely related to mineralization of organic carbon. Samples of cinnamon soil were prepared into slurry and then incubated anaerobically in dark or under illumination, to study effect of illumination on iron oxides reduction. Water soluble inorganic carbon and total water soluble carbon were analyzed simultaneously to explore relationship between anaerobic redox of iron oxides and carbon transformation under illumination in cinnamon soil. Results show that 55.31% of the free iron oxides in the soil could be reduced anaerobically under dark regime, and only 38.90% could under illumination. As Fe(II) produced anaerobically could be oxidized by oxygen generated by photosynthesis of cyanobacteria, the reduction rate of free iron oxides was found to be lowered to 7.95% after 40 days of anaerobic incubation under illumination. The content of soluble total carbon and soluble inorganic carbon increased by 69% and 246%, respectively, after 40 days of anaerobic incubation in dark, while they both displayed a rising-and-then-declining trend during anaerobic incubation under illumination. When the 40 days of incubation ended soluble total carbon and inorganic carbon was found only 47% and 70% higher, respectively, than it was at the beginning of the incubation The content of soluble total carbon was closely related to the content of 0.5 mol L^-1 HCl extractable iron, while the content of soluble inorganic carbon was to the content of Fe(II) in the soil under the incubation.