<p>With the rapid development of micro/nano-electromechanical systems (MEMS/NEMS), the issue of thermoelastic coupling and buckling in micro/nano-structures has become a key area of research. The classical continuum mechanics theories struggle to effectively detail the mechanical characteristics of micro/nano-structures under non-uniform temperature distributions, the current research primarily concentrates on the micro-scale effects of single strain fields, with limited analysis on the combined impacts of thermal and mechanical nonlocal effects. This paper explores the thermomechanical buckling of micro/nano-beams under nonuniform temperature distributions using nonlocal strain gradient theory with thermal considerations. The study finds that nonlocal effects in micro-scale phenomena lead to a decrease in critical load, while higher-order strain gradients tend to increase the critical load. Additionally, thermal effects also contribute to an increase in critical load. It is known that buckling can affect the load-bearing capacity and stability of a structure, thereby ensuring the safety and reliability of structures in engineering. The present study focuses on enriching micro-scale theories for stability analysis of micro/nano-scale structures, consequently offering valuable insights for enhancing structural stability and optimizing the performance of micro/nano devices.</p>