The practical operation of large-scale photovoltaic (PV)-concentrated solar power (CSP) hybrid power stations is faced with internal and external voltage problems after they are connected to the power grid. This is affected not only by the voltage state of the nodes inside the station, but also by the stability state of static voltages of the external power system. To address these problems, this paper proposes a two-stage optimal reactive power control method considering internal-external dual voltage security of the PV-CSP hybrid power station. First, the voltage security state of the hybrid power station is characterized by three indices: the margin of static voltage stability, the degree of node voltage balance, and the margin of reactive power reserve. Second, based on the information of long-term hourly PV output forecasts, the slow adjustment of on-load tap changer and capacitor banks is implemented in stage I. For the fluctuation of PV output at the short-term minute level, the PV and CSP power generation units and the static synchronous compensators within the hybrid power station serve as the control targets for optimization in stage II, intending to achieve rapid and precise voltage regulation. The proposed method effectively avoids the frequent optimization and regulation of all station equipment, thereby improving control efficiency. Finally, the analysis results on the test system demonstrate that, through the coordination of two-stage reactive power controls, the proposed method can mitigate the impact of PV power output fluctuation and reduce the over-limit risk of station voltage security and the risk of voltage instability.