Stimuli-responsive camouflage systems with printable architectures and long-term stability are of paramount importance in advanced military applications. In such adaptive camouflage devices, the stimulus-responsive layer that modulates chromatic properties plays a pivotal role. A critical challenge in electrothermal-actuated camouflage systems lies in mitigating the aggregation and enhancing the temporal stability of solution-processed silver nanowires (AgNWs) employed as the active stimulus layer. Herein, we report a rationally designed composite system comprising AgNWs and hydroxypropyl methylcellulose (HPMC), which demonstrates significantly enhanced electrothermal efficiency and operational stability through synergistic thermal management and intermolecular engineering. The incorporation of cellulose matrices in the AgNWs/HPMC composite exhibits substantially lower thermal conductivity compared to AgNWs networks, effectively reducing the heat-transfer coefficient of the electrothermal system. This modification facilitates controlled thermal dissipation from the heating element to the ambient environment, substantially augmenting the electrothermal conversion efficiency. Moreover, the molecular-level interactions between the hydroxyl moieties (C-OH) of HPMC and the carbonyl groups (CO) of AgNWs significantly enhance the spatial uniformity and temporal stability of the electrothermal system. Quantitative analysis reveals that the AgNWs/HPMC heater achieves a 163.2 % increase in temperature elevation compared to conventional AgNWs heaters under identical conditions (3 V, 90 s). The optimized composite system maintains consistent electrothermal performance over 138 days under atmospheric conditions, whereas the control system exhibits complete performance degradation within 5 days. Furthermore, we demonstrate an all-printable multilayer biomimetic device incorporating the AgNWs/cellulose composite as the thermal stimulus layer, achieving rapid chromatic modulation (<
5 s) at ultra-low operating voltages (<
1 V) for efficient environmental adaptation. This work establishes both theoretical foundations for high-performance, stable printable electrothermal materials and provides innovative strategies for fabricating next-generation adaptive camouflage systems.