To address the requirements for automatic control of pressurizer steam-space formation (i.e., the establishment of a steam space within the pressurizer) during the startup process of pressurized water reactor (PWR) nuclear power plants, this study conducted simulation modeling, control logic implementation, and optimization research on the steam-space formation process. A comprehensive simulation verification platform was developed using the RELAP5 thermal-hydraulic program, the 3KeyMaster simulation platform, and MATLAB/Simulink control modeling tools, achieving high-fidelity modeling and real-time interactive simulation of the reactor coolant system and its associated auxiliary systems. On this platform, intelligent closed-loop control strategies for pressurizer pressure and liquid level were designed, alongside automated sequential control logic covering the entire steam-space formation procedure. Coordinated control of the pressurizer electric heaters and spray valves, as well as automatic interaction among related systems including the Chemical and Volume Control System (RCV) and the Residual Heat Removal System (RHR), were successfully implemented. Simulation tests validated the effectiveness of the proposed control scheme, demonstrating that the automated system could reliably establish the steam space according to predefined procedures and smoothly elevate primary loop pressure to the target level, significantly reducing manual intervention. Sensitivity analyses and optimization studies were also performed on critical parameters within the control scheme, such as the heater activation and deactivation temperature thresholds. The optimized scheme showed a substantial reduction in pressure overshoot and shortened the steam-space formation duration, providing technical reference and support for achieving future “one-button startup” functionality in nuclear power plants.