Electromagnets, serving as core hydraulic components in electro-hydraulic control systems, are widely applied in aerospace and petroleum industries. The operational generation of Joule heat and electromagnetic loss results in rapid temperature increase, local thermal stress and uneven expansion deformation, significantly affecting stability and service life. The evolution of temperature, stress and deformation in the electromagnet was studied using finite element software, and the influence of heat dissipation, with considering both heat conduction sleeve and forced convection, on its thermal performance was analyzed. The results show that the maximum temperature, thermal stress and deformation of the electromagnet exhibit a linear increase with the increase of the coil power. Additionally, the steady-state maximum temperature, deformation and thermal conductivity demonstrate a linear decrease with an increase in sleeve thickness, with the temperature drop recorded at 12.5 ℃/mm. Moreover, as the flow rate rises, there is a notable decrease in maximum temperature, thermal stress and deformation, within a temperature drop range of 45.5 ℃/(m·s^-1). This indicates that both enhanced heat conduction and convection contribute to improving the thermal performance of electromagnet, with convection exhibiting a more significant effect.