A rationally designedflexible electrothermalfilm is composed of Super-P (SP, nanoparticle),thermoplastic polyurethane (TPU) and silica. The electric heating behavior of electrothermalfilmscan be facilely adjusted by SP contents and applied voltages. TPU/SP composite with 25 wt.% SP presentsrobust structural stability, fast response feature and superior electrothermal reproducibility. Theconductive network formed by SP nanoparticles not only could quickly convert the electric energy toheat, but also is stable under stepwise periodic and long-term electric heating–cooling conditions. Finally, a smart wrist band integrated electric heater and temperature indicator is verified the highpotential in multifunctional wearable device applications.