In order to reveal the effect of cadmium stress on crop physiological characteristics，the changes of Cd content，photosynthetic parameters，endogenous hormones and growth parameters in soybean seedlings under cadmium stress and the physiological mechanism of endogenous hormones regulating stomatal aperture and photosynthetic carbon assimilation under cadmium stress were carried out. The results showed that，cadmium stress could lead to the increase of ABA content and the decrease of ZR content in leaves，the increased ABA/ZR could induce stomatal closure. After the initial Cd treatment，stomatal conductance，photosynthetic rate，intercellular CO₂ concentration showed a trend towards reduction，which indicated that stomatal limitation was the main factor inhibiting photosynthesis. With the increase of cadmium treatment time，the content of cadmium ion in leaves increased gradually，which could cause ion toxicity to mesophyll cells. After 9 days of Cd stress，stomatal conductance and photosynthetic rate decreased，but the intercellular CO₂ concentration showed an increase trend. Thus，non-stomatal factors were the main factors limiting photosynthesis. Finally，the plant height，leaf area and root dry weight of soybean seedlings were significantly reduced under long-term cadmium stress.