The environmental simulation experiment of gleyed paddy field was carried out in net lab in order to explore the effect of slow-release calcium peroxide on the improvement of gleying paddy soil. Four kinds of slow-release calcium peroxide were selected from 10 kinds of coated slow-release calcium peroxide. The total content of reducing substances in the soil of gley fertile paddy field was investigated in rice tillering and harvest stages, and the changes of active reductive substances, reductive ferromanganese, effective nutrients and the dynamic changes of soil pH, redox potential and reactive oxygen concentration during the whole growth period of rice were also studied. The results showed that calcium peroxide could reduce the contents of soil reduction substances in the sampling period, and could improve the contents of available nutrients and soil pH, redox potential and reactive oxygen concentration in soil. Slow-release calcium peroxide had the best effect, followed by calcium peroxide granules and powders. The effect of ethyl cellulose coating was the best in the treatment of slow-release calcium peroxide, compared with the treatment of ethyl fiber coated calcium peroxide and calcium peroxide powder, the total content of reducing substance, the contents of active reductive substance, reductive iron and manganese were reduced by 22.9% and 36.0%, 20.6% and 13.6%, 37.6% and 29.0%, 38.7% and 56.9% in tillering stage respectively, decreased by 32.4% and 20.0%, 32.7% and 19.5%, 34.3% and 7.9%, 25.5% and 38.6% in harvest stage respectively; soil pH increased by 13.5% and 8.3% respectively, soil redox potential and reactive oxygen concentration increased by 43.0% and 2.2%, 58.6% and 13.4% respectively. The above results can provide theoretical and practical basis for the improvement of gleying paddy fields by slow-release calcium peroxide.