ABSTRACT This study developed a polydopamine (PDA)‐modified ultra‐high‐molecular‐weight polyethylene (UHMWPE) fiber‐reinforced thermoplastic polyurethane (TPU) composite hose with a variable diameter to address the limitations of single‐interface design and insufficient pressure resistance in conventional fire hoses. First, UHMWPE fibers were functionalized with PDA to enhance their interfacial adhesion with the TPU matrix. Subsequently, the modified fibers were fabricated into preforms and combined with TPU inner tubes via hot‐pressing to produce novel variable‐diameter hoses. Multiple hose specifications were designed and manufactured to systematically evaluate interfacial bonding strength, pressure resistance, and failure mechanisms. The results demonstrate that precise control of PDA modification parameters and hose structural design significantly improve both interfacial bonding and pressure resistance. This work provides an innovative strategy for fabricating multi‐interface, high‐pressure‐resistant fire hoses with enhanced adaptability.