The aim of this research was to study the influence of different culture conditions on the expression of Vi capsular polysaccharide and the effect of Vi capsular polysaccharide in the viability of Salmonella enterica serovar Typhi (S. Typhi) in macrophages. S. Typhi was cultured in LB medium under different stresses or in different media, and real time fluorescent quantitative reverse transcription polymerase chain reaction (real time RT­PCR) was used to detect the transcription of Vi­related genes and flow cytometry was used to analyze the expression of Vi. Macrophages were infected with wild type (WT) strain and Vi mutant strain (ΔvexE) to observe the effect of Vi in the viability of bacteria. The results showed that the expressions of tviA, tviB and vexE were down­regulated in responses to oxygen, Mg^2＋and antimicrobial peptide stresses, and up­regulated under acid stress, and in SOB, LPM, M9 media. Except for oxygen stress, the results of flow cytometry were consistent with real time RT­PCR. The survival rate of ΔvexE strain in macrophages was significantly lower than that of WT strain. It is concluded that acid stress, SOB, LPM and M9 media promote Vi expression. Mg^2＋ and antimicrobial peptide stresses inhibit Vi expression. The influence of oxygen stress on Vi expression is still unclear. Vi could enhance the intracellular survival of S. Typhi in macrophages.