Abstract: Coupling of the Monte Carlo (MC) method and the discrete ordinate (SN) method is studied. An SN-MC coupling scheme is adopted in order to eliminate low sampling efficiency of the MC method and difficulty in complex geometrical modeling of the SN method. In the coupling method, the SN code provides neutron angular flux, and a coupling program is used to calculate probability distributions of surface sources. A modified source sampling subroutine is used to produce a combined surface source which contains bottom, top and side surfaces at the same time, and then a Monte Carlo calculation is performed. Preliminary numerical results demonstrate that the coupling method is correct and it can be used in pressurized water reactor cavity radiation streaming calculation.