It has been shown that flexible pressure sensors may be used in many different contexts, including human-machine interaction, intelligent robots, and health monitoring. In this work, we create a 3D sponge piezoresistive pressure sensor using MXene, chitosan, polyurethane sponge, and polyvinyl pyrrolidone (MXene/CS/PU sponge/PVP), with the well-conductive MXene nanosheet serving as the force sensitive material. In particular, the mechanical strength and endurance of the sensor are enhanced by electrostatic self-assembly between the negatively charged MXene nanosheets and the positively charged CS/PU composite sponge skeleton. The insulating PVP nanowires (PVP-NWs) also crease the device's initial current, increasing the sensor's sensitivity. These characteristics allow the pressure sensor to simultaneously have a high sensitivity (50.27 kPa -1 for pressure below 7 kPa and 13.3 kPa -1 for pressure between 7 and 16 kPa), a quick response time (160 ms), a short recovery time (130 ms), and excellent cycling stability (5000 cycles). Moreover, the sensor exhibits a waterproof performance, where the force-sensitive layer still works normally after cleaning. In practice, the sensor could detect a variety of human actions as well as the distribution of spatial pressure due to the above superior device performance.