Abstract: Developments and applications of Monte Carlo method in reactor physics analysis are limited due to large memory demand, while domain decomposition method (DDM) is one of feasible solutions under research. Basic idea of DDM was introduced in this article and applied into Monte Carlo neutron transport process. A DDM module was implemented based on a reactor Monte Carlo code RMC. By numerical tests, the performance of DDM was evaluated. The results show that load balancing and parallel communication are key factors for parallel efficiency. An approach by sorting source neutrons was proposed to achieve reproducibility of calculations with DDM.