Concrete filled steel tube (CFST) mixed structure has become one of the most preferred options for the main bearing structural system of domestic bridge constructions in highly seismic regions, due to the high performance contributed by the optimized mixture of CFST members and concrete or steel members.This paper outlines the mechanism and design theory of two kinds of CFST mixed structures, i.e., trussed CFST structure and concrete-encased CFST structures. The former refers to a truss structure formed through the mixture of CFST chord members and steel tubular brace members while the latter refers to a box hollow structure formed through the mixture of trussed CFST structure and encasing concrete. The corresponding practical applications in mega bridge practices, together with the future prospects of CFST mixed structures, are also discussed.