<p>Currently, ship plate steel is mainly prepared through the thermomechanical control processing (TMCP), as this process is beneficial for improving the mechanical properties. Investigating the hot deformation behavior and constructing hot processing maps hold significant implications for designing and optimizing the TMCP process. In this study, the thermal deformation behavior, hot processing map, and microstructural evolution of EH40 ship plate steel were systematically investigated through hot compression experiments under deformation temperatures of 900-1150 °C and strain rates of 0.01-10&#xa0;s⁻¹. The results indicate that the flow stress of EH40 ship plate steel decreases with increasing deformation temperature and increases with increasing strain rate. The thermal deformation activation energy (<i>Q</i>) of EH40 ship plate steel was calculated as 364.905&#xa0;kJ/mol, and an Arrhenius-type constitutive model was established. Based on the hot processing map, the optimal hot deformation window is 1050-1150 °C/1-10&#xa0;s⁻¹. The post-deformation microstructure is composed of a mixture of upper bainite, lower bainite, and granular bainite, and the length of bainitic ferrite laths decreases with increasing strain rate but increases with rising deformation temperature. Moreover, the formation of lower bainite can be promoted by increasing the deformation temperature or strain rate.</p>