This study investigates the cavitation phenomenon at the DVI nozzle in pressurized water reactor (PWR) nuclear power plants. Cavitation refers to the process of localized liquid vaporization when the local pressure drops below the critical pressure corresponding to the size of existing gas nuclei, leading to the formation and subsequent collapse of vapor bubbles. While cavitation can cause adverse effects such as cavitation erosion and noise, it also serves a protective function by restricting flow and safeguarding equipment. In PWRs, Venturi-type DVI nozzles are used to prevent the rapid discharge of high-energy fluid from the reactor pressure vessel into the containment in the event of a DVI pipeline rupture. However, during safety injection, cavitation can affect the safety injection flow rate and thus impact the consequences of accidents. This research first employs Computational Fluid Dynamics (CFD) to simulate cavitation experiments with Venturi nozzles, verifying the rationality of the cavitation model and parameter settings in CFD simulations. Subsequently, thermal–hydraulic analysis software is used to calculate boundary conditions such as pressure upstream and downstream of the DVI nozzle during accident transients. Based on these data, cavitation phenomena at different DVI nozzle structures are simulated. The results indicate that a well-designed nozzle structure can prevent cavitation, ensuring stable safety injection flow rates and enhancing the safety of nuclear power plant operations.