In order to explore the degradation rules and nutrient release characteristics of silicon fertilizer on the growth of Crotalaria pallida and Sorghum sudanense，and under the conditions of natural returning to the field，experiment was conducted to explore the effects of silicon fertilizer on the growth，nutrients content and organic carbon degradation law，nitrogen，phosphorus，and potassium nutrients release characteristics at 3～168 d after the returning of Crotalaria pallida and Sorghum sudanense to field under natural conditions through nylon mesh bag method.The result showed that，compared with no silicon treatment，42.4 kg/hm² silicon fertilizer(SiO₂)significantly increased the yield of two green manures by 27.87% and 24.90%，nutrient(N+P+K)accumulation by 30.60% and 28.80% ，silicon concentration by 82.75% and 29.15%，respectively，and increased the nitrogen content of Crotalaria pallida by 15.79%，potassium content of Sorghum sudanense by 7.51%.Silicon fertilizer suppressed remarkably two manure’s organic carbon degradation，nitrogen releasing and dry matter degradation of Crotalaria pallida after returning to field 3～56 d under natural conditions.At 56 d after manure returning to field，two manure’s organic carbon degradation decreased by 8.90% and 7.46%，nitrogen releasing decreased by 7.85% and 12.11%，respectively，and dry matter degradation of Crotalaria pallida decreased by 12.53%，compared with no silicon treatment.There was no distinct change in degrading characteristics for two green manures with silicon fertilization，but dry matter and organic carbon degrading acceleration for Sorghum sudanense was higher than that of Crotalaria pallida，and nitrogen，phosphorus and potassium releasing rate at 28 d after returning to field was 5.80～18.13 percentage points higher.These results could provide important basis to improve the effect of green manure cultivation soil fertility.