Abstract: The self-developed COSINE Monte Carlo code cosRMC is designed for the analysis of the reactor core and the radiation shielding. The typical functions as transport simulation, burnup calculation, group constants generation, sensitivity & uncertainty analysis and visual modeling have been sufficiently researched. A lot of V&V work was carried out, and the recent application in AP1000 PWR and China Fusion Engineering Test Reactor (CFETR) is introduced in this paper to show the capability of cosRMC. The simulation results show the maximum absolute deviation is 89.9 ×10^-5 for eigenvalue and 2.1% for power distribution of the 21 types of assemblies and core models of AP1000, while the maximum absolute deviation is 0.6% of the CFETR thorium proliferation ratio. The typical work further exhibits that cosRMC software can meet the computational needs of the large and complex models such as PWR and Fusion Reactor with high accuracy, and the visual modeling tool imbedded can effectively improve the modeling efficiency.