Abstract <p>Currently, most of the available methods are focused on the SIF calculation of single cross-crack under single stress loading, without consideration of the thermal-mechanical coupling loadings. To capture the true coupling impact of the temperature and stress fields, based on the Williams expansion and semi-weight function method, a semi-analytic method is presented to calculate the thermal-mechanical coupling cross-crack SIF under arbitrary boundary conditions. The existing results are used to validate the method and several examples are given to analyze the influence of crack length, temperature and boundary on the cross-crack SIF under thermal-mechanical coupling. Results show that when <i>L</i>/<i>a</i> (the ratio of the rectangle length to the crack half-length) and <i>H</i>/<i>a</i> (the ratio of the rectangle width to the crack half-length) increase, Mode I fracture is more likely to occur. The increase of plate size only changes the SIFs, but not the stress distribution of coupling field. The effect of circular boundary on crack tip stress field is greater than that of rectangular boundary.</p>