Abstract: In order to study the regulatory effect of DA-6 on different soybean varieties in South China, we selected 4 soybean varieties Zhongdou 41, Wandou 28, You6019 and Zhongdou 63 with different genotype for study, sprayed DA-6 on the leaves during the initial bloom stage and seed filling stage, and studied the effects of DA-6 treatment on photosynthetic characteristics, agronomic traits, yield and its components, and quality of soybean. The results showed that DA-6 could improve the chlorophyll content, photosynthetic rate, water use efficiency and stomatal conductance of different soybean varieties in South China, and then regulate photosynthesis. There were differences in agronomic traits, yield components and quality traits among varieties treated with DA-6. The plant height decreased and the nodes number of main stem increased in all cultivars. The plant height of high protein variety Wandou 28 decreased the most, and the plant height of low variety Wandou 41 decreased the lest, and the nodes number of main stem of high protein variety Wandou 28 increased the lest. The yield components different of varieties improved, and the yield of Zhongdou 63, Wandou 28, Zhongdou 41 and You 6019 increased by 9.5%, 8.8%, 10% and 2.7% respectively. After treated with DA-6, the protein content of Zhongdou 63, Zhongdou 41 and You 6019 decreased by 0.2%, 0.4% and 0.3% respectively, but the protein content of Wandou 28 didn’t change, the fat content of Zhongdou 63 decreased by 0.2%, the fat content of Wandou 28 didn’t change. The fat content of Zhongdou 41 and You 6019 increased by 0.4% and 0.1% respectively. The changes of yield, protein and fat content in different cultivars was different from the changes of agronomic traits after treated with DA-6. The results showed that DA-6 treatment promoted the yield of southern soybean varieties, and had different effects on photosynthetic, agronomic and quality traits of different varieties. The effects on photosynthetic traits, agronomic traits, yield and quality of southern soybean varieties with different specific of DA-6 treatment were different.