Flexible pressure sensors with high sensitivity are required in fields such as human-machine interactions, electronic skin, and health tracking. In this work, we reported cellulose ion-conductive hydrogel (ICH) rationally designed from both nano and micron perspectives for ultrasensitive pressure sensors, via a zero-waste approach, without involving soft components. By introducing low molecular weight cellulose and using the idea of a rough surface, the piezocapacitive sensitivity of the ICH was increased from 0.04 kPa-1 to 89.81 kPa-1 in increments of 2245, which also has a high degree of transparency, excellent durability, and good electrical transmission. Moreover, the ICH demonstrated great potential as sensors and arrays practicable in various industries, including medical treatment and motion recognition. The design is also applicable for piezoresistive tactile sensors, which realize enhanced sensitivity. This affordable, effective, and environmentally friendly technology definitely offers novel perspectives and the potential to enhance the functionality of flexible pressure sensors.