Due　to　the　need　for　high　accuracy　and　more　complex　core　geometry,　whole-core　transport　calculations　with　the　MOC　are　demanded.　Recently,　a　2D+1D　method　has　been　proposed　to　perform　3D　whole-core　transport　calculations,　but　it　is　not　easy　to　apply　this　method　to　the　cases　with　complex　geometry　in　the　axial　direction.　Direct　3D　MOC　calculations　are　thus　required.　This　approach　is　however　limited　by　the　amount　of　computer　memory　which　is　required　for　the　ray　tracing　data　that　is　required　by　the　MOC.　This　paper　presents　a　modular　tracing　technique　and　corresponding　angular　quadrature　sets,　which　can　greatly　reduce　the　amount　of　ray　tracing　information,　making　it　practical　for　the　MOC　to　deal　with　the　large　3D　problems.　In　this　paper,　we　introduce　the　model　of　the　modular　ray　tracing　technique　and　give　some　results　of　our　method.