Abstract: Reactor pressure vessel (RPV) is an irreplaceable component in pressurized water reactors. It carries internal components, fuel assemblies and primary cooling water. Its integrity plays an important role in the safe operation of the reactor. Microscopic defects caused by neutron irradiation can cause radiation hardening and radiation embrittlement of RPV steel, increasing the risk of brittle fracture of RPV steel. Accurately characterizing the microscopic defects is of great significance for predicting the macroscopic properties of RPV steel. Solute defect clusters are the dominant radiation defects in RPV steel. Because they are rich in solute atoms Cu, Mn, Ni, etc., they can also be called Cu-rich precipitates and Mn-Ni-rich precipitates. At present, there are few studies on the nucleation and growth of precipitates dominated by vacancy clusters. Due to the limitations of microscopic characterization technology, it is difficult to directly observe solute-vacancy clusters in RPV steel. In this work, the solute-vacancy clusters generated in RPV steel after irradiation were focused. Taking the FeCuMnNi alloy system as the research object, the nucleation and growth process of solute-vacancy clusters were explored. The Metropolis Monte Carlo method was used to simulate the stable configurations of the solute-vacancy clusters in different RPV model alloys. The molecular statics method was used to study the interaction mechanism between solute atoms and vacancy clusters. The results show that in FeCuMnNi alloy system, Cu atoms preferentially segregate on the surface of vacancy clusters than Mn and Ni atoms, and the solute-vacancy clusters have a spherical shell structure. Mn can promote the growth of solute-vacancy clusters, while Ni has little effect on the growth of solute-vacancy clusters. Mn and Ni elements have a synergistic effect, which can promote the growth of solute-vacancy clusters. There is a correlation between the structure and energy of solute atoms in solute-vacancy clusters. Vacancy clusters can directly change the structures of solute atoms nearby, causing the inner solute atoms have significantly higher energy than the outer atoms. The growth process of solute-vacancy clusters can change from being dominated by vacancy clusters to outer solute atoms. The results are helpful to understand the formation and evolution behaviors of microscopic defects in RPV steel under neutron irradiation, and promote the prediction of irradiation embrittlement. In the future, to fully reveal the nucleation and growth process of solute-vacancy clusters, we will carry out research from a kinetic perspective using the kinetic Monte Carlo method or the cluster dynamics method.