Reduced activation ferritic martensitic (RAFM) steel has been regarded as a candidate for blanket material of nuclear fusion plant. Microstructure of RAFM steel, featured by precipitates and hierarchical structure of martensite, contribute to its excellent irradiation resistance. For better understanding of mechanical responses of RAFM steels, microstructure-based simulation has been developed for describing detailed elastic-plastic behavior in grain (or meso-) scale. In this study, a dislocation density based crystal plasticity model including dislocation-precipitate interactions was proposed and implemented in the finite element simulations of meso-scale micropillar compression and macro-scale uniaxial tensile tests. For the macroscale simulations, a representative volume element approach with periodic boundary condition was applied for predicting mechanical response of investigated polycrystalline RAFM steel based on measured mesoscale parameters and microstructure. The presented crystal plasticity model could reproduce the mesoscopic local deformation and macroscale flow stress strength in good agreement.