Abstract: Taking cucumber‘Jinlyu 21-10’as test material,pot experiments were conducted,the effects of different Si concentrations on cucumber seedling growth,photosynthetic parameters pigment content,chlorophyll fluorescence parameters and photosynthetic parameters in calcareous cinnamon soil under different Cd concentrations were studied,in order to explore the mitigation effect of silicon on cadmium toxicity.The results showed that Cd stress affected cucumber seedling growth,photosynthetic pigment content of functional leaves,chlorophyll fluorescence parameters and photosynthetic parameters.Silicon intervention increased cucumber seedling growth,photosynthetic pigment content,actual photosynthetic quantum yield of PSⅡ （Y（Ⅱ））,photochemical quenching coefficient（qP）,net photosynthetic rate（Pn）,transpiration rate（Tr）,stomatal conductance（Gs）,and decreased initial fluorescence（Fo）,intercellular carbon dioxide（Ci）.The maximum photochemical efficiency（Fv/Fm）of PSⅡ was not significantly affected by cadmium stress at higher concentration of silicon(Si≥300 mg·kg^-1),and Fv/Fm tended to be stable.The protective mechanism of carotenoids in Cucumber functional leaves was demonstrated by the intervention of silicon concentration from100 mg·kg-1 to 300 mg·kg^-1.Under high concentration cadmium(5 mg·kg^-1)stress,silicon concentration(Si≥200 mg·kg^-1)was required to reflect the alleviation effect on physiological indexes of cucumber seedling.It indicated that silicon intervention could alleviate the toxicity of cadmium stress on physiological characteristics of cucumber seedling,improve the photosystem Ⅱand photosynthesis of cucumber seedling leaves under cadmium stress,and apply appropriate amount of silicon fertilizer could inhibit and alleviate the cadmium toxicity of plants in cadmium-contaminated soil.