Rcs is a complex two-component system in Enterobacteriaceae bacteria. It regulates the synthesis of bacterial colanic acids, and the expressions of bacterial flagella genes and resistance genes. Distinguished with typical two-component systems, Rcs consists of three components, among which phosphate group is transferred via three steps. Rcs in different species may possess its own distinct functions, mainly in the regulation of bacterial virulence and stress control. This review focuses on the components, function and signal transduction mechanisms of Rcs system.