Abstract: As an important deterministic method for the neutron transport problem, the method of characteristics (MOC) has many advantages of strong geometric adaptability, simple calculation diagram, and easy large-scale parallel. ANT-MOC is a self-developed three-dimensional MOC neutron transport code in the China Virtual Reactor 1.0 (CVR1.0), which is mainly used for steady state core transport calculations of pressurized water reactor (PWR) and fast breeder reactor (FBR). ANT-MOC supports complex geometric modeling based on constructed solid geometry (CSG), efficient user input methods, ray tracing algorithms for rectangular/hexagonal grids and parallel algorithms and load balance based on trajectory chain decomposition. On domestic supercomputers in China, ANT-MOC can scale to about 100 000 processor cores to reach a parallel efficiency above 50%. The verification and parameter sensitivity analysis were conducted with PWR and FBR core calculation problems. The results show that the calculation results of ANT-MOC can achieve good stability and accuracy.