With the rapid development of communication technologies and portable flexible electronic devices, the problems related with electromagnetic radiation and heat accumulation have been increasingly aggravated, posing significant threats to surrounding electronic equipment and human health. Therefore, the development of flexible multifunctional composite films with high electromagnetic interference (EMI) shielding performance and excellent fire safety has been considered an urgent necessity. In this study, a multifunctional tunable sandwich-structured composite film was successfully prepared, comprising polyvinyl alcohol-ammonium polyphosphate (PVA-APP) as a flexible flame-retardant outer layer, a silver nanowire (AgNWs) conductive network as the inner layer, and polydimethylsiloxane (PDMS) as the encapsulation layer. The composite film exhibits outstanding performance in electromagnetic shielding, flame retardancy, and hydrophobicity. The sandwich structure was designed to significantly enhance the shielding stability of the internal AgNWs layer. When the carrying capacity of the AgNWs is 0.50 mg/cm², the EMI shielding effectiveness of this film reaches 53.12 dB. Furthermore, the vertical burning test results in accordance with UL-94 standard reveal that the composite film also exhibits self-extinguishing property with a V-0 flame-retardant grade. Additionally, the PDMS encapsulation layer endows the composite film excellent hydrophobicity and self-cleaning properties, even when the film was subjected to bending or placed in a humid environment its EMI shielding performance remains stable. In conclusion, the film is characterized by its simple fabrication process and excellent comprehensive performance, making it highly promising in applications for components with curved surfaces and flexible foldable electronic devices.