An electric power system is an important factor in national economic development. However, as an electric power system requires more electric equipment in its operation process, it is prone to short circuits, faults and other problems, which can lead to fires. To help prevent fires in such power systems, the hydraulic performance of the existing firefighting monitor should be optimized. A rectifier is an important structure which affects the performance of the firefighting monitor. In this paper, numerical simulations based on CFD (computational fluid dynamics) are carried out to analyze the fluid flow inside firefighting monitors with five different rectifier structures. In addition, the effects of rectifier structure on both the turbulent kinetic energy and axial velocity of the fluid inside the firefighting monitor are analyzed. The results show that rectifier installation can reduce the turbulent energy of the inlet and outlet of the firefighting monitor and improve the axial velocity distribution inside the firefighting monitor. Specifically, a forked row rectifier arrangement can significantly improve the effect of flow stabilization. However, there are limits to improving rectifier stabilization performance by changing the number of blades, as too many blades can cause reverse direction flow and large pressure losses.