Abstract: Flexible capacitive pressure sensors are highly promising for applications in smart wearable devices, yet their performance remains constrained by interfacial electrical properties and structural design limitations. In this study, we developed a three-dimensional fibrous network dielectric substrate via a needle-punching and thermal bonding process. The substrate underwent surface modification through low-temperature plasma treatment and was subsequently functionalized with ionic liquids. Utilizing copper foil as the electrode, we designed a capacitive pressure sensor based on the ion-modified three-dimensional fibrous network structure.The performance of the sensor was comprehensively evaluated through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), fourier transform infrared spectrometer (FTIR), mechanical and physical property testing, electrical performance assessment, and human-body application experiments. The experimental results demonstrate that the sensor exhibits a high sensitivity of 1.83 kPa ⁻¹, which is 5.4 times greater than that of capacitive sensors without plasma treatment, and 20.3 times higher than that of sensors without ionic liquid modification. Additionally, the sensor possesses rapid response and recovery times (170 ms and 110 ms, respectively), a wide detection range (0–255.92 kPa), and excellent cyclic stability. In practical applications, the sensor effectively detects subtle human motion signals, such as swallowing, pressing, and grasping, showcasing its significant potential for applications in health monitoring, human-machine interfaces, and related fields.