Abstract: Taking the square pepper ‘Mandi’ as test material, the experiment method in the solar greenhouse was used to study the effects of increased CO₂ application on pepper morphology, chlorophyll content, ribulose-1,5-bisphosphate carboxylase activity, net photosynthetic rate and pepper fruit yield and quality under low temperature, in order to provide reference for improving pepper yield and quality in facility agriculture.The results showed that, 1) adding CO₂ alone, the growth of peppers was the best, and the morphological index, photosynthetic parameters, fruit size, single fruit weight and total weight of pepper all reached the maximum.2) With the low temperature treatment alone, the growth of pepper was the worst, and the morphological indicators, photosynthetic parameters, fruit size, yield and quality were significantly reduced.3) Compared with the low temperature treatment alone, the increased CO₂ treatment at low temperature significantly improved the growth of peppers, and the fruit size, yield and quality of peppers were significantly improved.Adding CO₂ treatment at low temperature could alleviate the stress of low temperature on the growth of peppers, which was beneficial to the growth of peppers, increased the yield of peppers, and improved the quality of peppers.