Abstract: The seedlings of summer squash were treated with low temperature, weak illumination and both low temperature and weak illumination. The photosynthesis parameters were determined to study the effects of low temperature and poor light stress on photosystem of squash leaves and the damaged condition of cells inside the blade. The results showed that under three stress conditions, the chlorophyll fluorescence parameters (Fv/Fm, NPQ), chlorophyll content, catalase (CAT) activity and superoxide dismutase (SOD) activity decreased to varying degrees, while malondialdehyde (MDA) and peroxidase (POD) activity increased to varying degrees. Among them, the chlorophyll fluorescence parameters decreased most under low light conditions, while both low temperature and weak illumination treatment could alleviate the damage of poor light to some extent. The physiological indicators of summer squash seedlings under weak light stress showed the most significant difference, indicating that weak illumination had the greatest impact on biofilm of summer squash.