Abstract: The multifunctional composites embedded with multi-walled carbon nanotube (MWCNT) interfacial sensor were manufactured, and its application in the in-situ monitoring of a filament wound pressure vessel was carried out. The reliability of the MWCNT interfacial sensor serviced in the complex environment was firstly considered. The effect of MWCNT on the interfacial shear strength (IFSS) was analyzed, and the water absorption characteristics of the composites with interfacial sensor in water were obtained. The in-situ monitoring and healing of interfacial damage were performed based on the embedded interfacial sensor, and the feasibility of this method was discussed. The MWCNT interfacial sensor was finally embedded into a filament wound pressure vessel, and the in-situ monitoring experiments of the vessel under hydraulic fatigue cycling and pressurization load were performed. The results show that IFSS could be enhanced by embedding MWCNT interfacial sensor, and its decreasing ratio shows a decreasing tendency in the special conditions. The interfacial damage in the thermoplastic composites could be successfully monitored and healed by the MWCNT interfacial sensor. The interfacial damage in the filament wound pressure vessel could also be in-situ monitored by the MWCNT interfacial sensor.