<p>Converting waste heat into usable energy holds profound scientific significance and broad applications in the energy conversion field. So far, considerable efforts have been dedicated to optimizing thermoelectric conversion based on the Seebeck effect. In the present work, we propose a distinct thermoelectric conversion mechanism that directly converts heat energy into electricity by harnessing thermal-driven piezoelectric effects within piezoelectric nanowires. We demonstrate the reliability of this mechanism through a simple lattice dynamics model, detailed molecular dynamics simulations, and finite element analysis. Our numerical simulations reveal that a temperature difference across the substrate induces pronounced periodic deflections in vertically standing GaN nanowires, generating a considerable output voltage on both sides of the nanowire. Furthermore, we demonstrate that gradient-structured nanowires exhibit more pronounced deflection than uniform nanowires under identical temperature conditions. Additionally, by adjusting the substrate thickness, the vibration direction of the nanowires can be precisely manipulated, paving the way for optimal regulation of the piezoelectric output voltage. This mechanism extends beyond GaN nanowires to other piezoelectric nanowire structures, unlocking a promising avenue for thermoelectric conversion distinct from the Seebeck effect.</p>