Topological insulator is a kind of phase of matter that is internally insulated and can conduct electricity on the surface. The energy band of a topological insulator has non-trivial topological characteristics, which supports a boundary state that can propagate in one direction. The appearance of topological states usually depends on the topological phase transition at the interface or boundary. Recently, a new topological π mode induced by gauge transitions has been successfully observed experimentally in Floquet systems, despite the same topological order across the whole lattices. In this paper, the origin of the topological π mode induced by the gauge field transition are discussed. The Hamiltonian of two Floquet systems with different gauges has opposite π gap mass terms due to gauge transition, thus leads to the emergence of interface states, which is similar to the Jackiw-Rebbi model. The research of this paper provides a theoretical basis for the generation of topological states from gauge transitions, and deepen the understanding of the Floquet gauge.