Steam power systems, as one of the critical power systems in industrial applications, require rigorous design and verification processes. Model-Based Systems Engineering (MBSE) provides a structured approach to decomposing system architecture from top to bottom and enabling multi-disciplinary collaborative design, ensuring precise requirement management and efficient design processes. To accelerate the iterative design and verification of steam power systems, this paper employs the SysML language to conduct requirement, functional, structural, and parametric analyses, thereby completing the system architecture design. The seamless transformation from system design architecture to system simulation architecture is achieved based on the SysML-to-Modelica tool. Additionally, Modelica simulation technology is utilized to construct simulation models and perform dynamic scenario analyses of the system. Innovatively, this paper proposes a closed-loop technical approach for steam power system design, simulation, and verification, which effectively optimizes system design and improves the efficiency of both design and verification processes.