The evolutionary behaviors of dislocations, sub-grain boundaries (SGBs), and precipitated carbide particles in 9Cr-1.7W-0.1C reduced activation ferritic–martensitic (RAFM) steel were studied by implementing varying levels of roll deformation and tempering processes. The microstructural parameters were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD). The relationships between these parameters, the deformation levels, and different tempering processes were quantitatively determined. The obtained results demonstrate that both high-level deformation and dual tempering (medium-temperature tempering T1 followed by standard tempering T2) contribute to the refinement of M23C6/MX particles, especially M23C6, due to the greater abundance of nucleation sites for M23C6/MX particles supplied by SGBs. How the correlation among these different microstructural parameters (dislocations, SGBs, and carbide particles) influenced the decreased process of engineering strength both at room temperature (RT) and high temperature was qualitatively and quantitatively discussed.