Wearable piezoresistive sensors play a crucial role in smart healthcare, motion tracking, and human-computer interaction, yet conventional materials often suffer from limitations such as low sensitivity, poor flexibility, and insufficient durability. To address these challenges, this study presented anisotropic porous composite aerogels (A₃₀-C₅S₅) fabricated through directional freeze-drying, incorporating silver nanowires (AgNWs) as a conductive network in combination with sodium alginate (SA) and carboxylate cellulose nanofiber (CNF-C) at an optimized ratio. The aerogel exhibited distinctive structural features: honeycomb-like dense pores in the XZ plane and a channel-type porous architecture in the XY plane. This unique structure enabled the A₃₀-C₅S₅ aerogel to achieve superior compressive strength (392.49 kPa) while maintaining notable resilience. Subsequently, polydimethylsiloxane (PDMS) was introduced through a vacuum-assisted impregnation process, resulting in an AgNWs/CNF-C/SA/PDMS composite aerogel elastomer that demonstrated high mechanical strength while preserving its porous framework. The piezoresistive sensor assembled with this elastomer exhibited exceptional performance characteristics, including a high gauge factor (GF = −3.622@0%–3%), rapid response capability (response/recovery time of 34/39 ms), and outstanding cycling stability (1000 cycles). Furthermore, when implemented as a wearable device, the sensor successfully achieved real-time, accurate monitoring of human joint movements. This work presents a novel approach for developing flexible electronic devices with significant potential applications in smart wearables, health monitoring, and human-computer interaction.