Multi-scale and multi-physical field topology optimization (TO) design has attracted large of attention, especially in aerospace and mechanical engineering, for the complex loadings and increasing performance requirements. Moreover, the unavoidable uncertainties, such as environment change, load variation, manufacturing tolerance, and elastic modulus fluctuation, exist in both macro- and micro-scale under coupled thermo-mechanical environment, which poses a significant danger for the safety of topological design of multi-scale structure in practical engineering. Therefore, a 2D multi-scale reliability-based topology optimization (MSRBTO) model is constructed to account for the uncertainty behavior of multi-physical TO problems, in which mechanical and thermal loadings are considered simultaneously. In addition, the solid isotropic material with penalization method is adopted at both macro- and micro-scales. Sensitivities of the compliance and temperature constraints with respect to the macro design variables, micro design variables, and random variables are derived simultaneously. Then, a single-loop method is introduced to address the MSRBTO problem to guarantee computational efficiency. Several numerical examples are solved by the developed MSRBTO method and traditional mono-scale RBTO method. The results show that the optimized results of the MSRBTO method show better performance than the mono-scale RBTO method, and the validity and effectiveness of the proposed method are validated.