Abstract: Through spraying silicon fertilizer in different periods, the effects of silicon fertilizer on sorghum production, photosynthetic rate and flexural strength were studied, to provide a scientific basis for silicon fertilizer application in sorghum. The "Return" brand liquid fertilizer was used in the test, randomized block design was adopted with a total of three treatments, and each treatment had three repetitions. The results showed that: spraying silicon fertilizer on sorghum could increase net photosynthetic rate and chlorophyll content, lower center of gravity height to improve stem flexural strength, and raise the content of grain starch, protein and fat. The effect of spraying silicon fertilizer at sorghum 10 leaf stage was the best.