Abstract: The objective of this study was to analyze the proportion of spleen regulatory T cells (Tregs) in chicks after Salmonella infection. In this study, Jing xing yellow chicken H lines were used as experimental groups, and 1-day-old chicks were randomly divided into control group (n=40) and infected group (n=80).Animals were kept in the same and sterile environment. At 7 days of age, the infected group was infected with Salmonella (Salmonella typhimurium CICC 21484) to establish an infection model. The control group was treated by saline instead of Salmonella. After 48 hours of infection, the expression levels of cecal tonsil immune response-related genes and serum inflammatory factors were measured in two groups. Then, two groups of chicks were randomly selected (control group, n=25; infected group, n=34) to detect CD4⁺ T cells and Tregs/CD4⁺T cells ratio of spleens. The results showed that there was no significant difference in the proportion of CD4⁺T cells in the spleens between control gruop and infected group (P>0.05). In infected group and control group, CD4⁺ CD25⁺/CD4⁺T cells (%) were 0.93±0.12 and 3.22±0.59, respectively (P< 0.01); CD4⁺ TGF-β⁺/CD4⁺T cells (%) were 0.55±0.07 and 1.42±0.25 (P<0.01), respectively; CD4⁺CD25⁺ TGF-β⁺/CD4⁺T cells (%) were 0.29±0.04 and 0.76±0.14, respectively (P<0.01), there were significant differences between the above data of the two groups. There was no significant difference in the proportion of CD4⁺T cells in the spleens of chicks after Salmonella infection. The ratio of Tregs/CD4⁺T cells were significantly lower than that in the control group (P<0.01). It is suggested that Tregs may be involved in the pathogenesis of Salmonella infection in chicks, which provides a theoretical basis for further study on the mechanism of chicks against Salmonella infection.