AbstractThis study reports a facile delignification and natural drying process for synthesizing cellulose films using the unique surface roughness, porosity, and lightness of the hollow stellate cellulose (HSC) united aerenchyma of the wetland weed Juncus effusus L. By controlling the grafted amino/fluorine‐bearing group content of various silane coupling agents, this work successfully manipulates the triboelectric polarities of HSC films after silanization. Subsequently, a layer of Ag nanowire electrodes is coated on one side of the silanized HSC friction layers, resulting in flexible, lightweight, semi‐transparent HSC‐based triboelectric nanogenerators (HSC‐TENGs) featuring both macro‐scale surface roughness and micro‐nano inner pores. These all‐in‐one HSC‐TENGs achieve the highest output voltage of 4.86 V, which is 28 times that of TENGs employing two pristine HSC films as triboelectric layers (PHSC‐TENG). Finally, the HSC‐TENG with the optimum output power is applied as a wearable self‐powered sensor for gait analysis, demonstrating stable and sustainable performances in distinguishing different body motions such as walking, running, jumping, and calf raising. This study not only proposes a new cellulose‐based TENG for future in‐depth body locomotion analysis but also paves the way for converting differently structured aerenchyma from abundant problematic aquatic or wetland weeds into promising structural templates in multifunctional cellulose‐based applications.