Abstract: In recent years, graphene oxide (GO) composites with both flame-retardant and early fire-warning functions have emerged as a new research field. To address the key issues of poor flame-retardancy and low sensitivity of GO, this paper proposes a solution of organic/inorganic coupling to synergistically improve the flame-retardant and fire-warning performance of GO composite films. Specifically, polyethyleneimine (PEI) is used to modify the surface of GO, and then it is compounded with MXene through electrostatic interaction to construct a PEI-GO/MXene composite film. The results show that: (1) When PEI burns, it generates a large amount of incombustible gases, while MXene is thermally oxidized to form TiO₂, which maintains the structural stability of the composite film. That is, PEI and MXene synergistically improve the flame-retardancy of GO through gas-phase and condensed-phase flame-retardant mechanisms. Compared with GO, the peak heat release rate of the PEI-GO/MXene composite film is reduced by 65%, and the char yield increases to 37.61%. Therefore, the fire-warning duration of this composite film can reach 180 s. (2) PEI reduces the oxygen-containing groups on the surface of GO through an amidation reaction, and the good electrical conductivity of MXene constructs an efficient electron-transfer path. With the help of these two factors, the fire-warning sensitivity of the PEI-GO/MXene composite film is significantly improved. The flame response time is only 1 s, and the response time at 300℃ is only 2 s.