Unlike nuclear main pump seals, deep groove seals in aero-engines operate on a contact basis. However, the precise working mechanism and accurate quantitative methods for assessing their sealing performance remain elusive. This paper introduces a fluid-solid-thermal coupling model for contact deep groove seals, utilizing a partition model and considering JFO boundary condition, mixed lubrication, and detailed heat calculations. The model significantly enhances accuracy compared to original approaches. It comprehensively accounts for contact effects, thermal deformations, convergence wedges, radial waviness, hydrodynamic pressures, groove drainage, and convection, revealing characteristics of contact deep groove seals such as high stiffness, effective heat dissipation, wear resistance, and prolonged service life. The proposed model and working mechanism provide theoretical guidance for designing diverse deep groove seal structures.