©　2017,　Science　Press.　All　right　reserved.Background:　Thorium-based　molten　salt　reactor　nuclear　power　system　project　is　one　of　the　leading　science　and　technology　projects　of　Chinese　Academy　of　Sciences,　its　strategic　goal　is　to　develop　the　fourth　generation　fission　reactor　nuclear　power　system.　The　core　of　solid　fuel　molten　salt　reactor　is　constructed　of　the　random　pileup　of　fuel　graphite　balls,　which　brings　difficulties　and　uncertainties　in　the　establishment　of　the　pebble　bed　model　for　simulation　analysis.　Purpose:　This　study　aims　to　analyze　the　influence　of　two　modes　of　fuel　ball　arrangement　on　the　core　flow　and　heat　transfer　in　the　molten　salt　reactor,　which　are　face　centered　cubic　(FCC)　and　body　centered　cubic　(BCC)　arrangement　mode.　Methods:　Based　on　the　computational　fluid　dynamics　(CFD)　program,　two　computational　models　based　on　the　FCC　and　BCC　arrangement　modes　are　established　respectively.　The　re-normalization　group　(RNG)　k-ε　turbulence　model　is　selected　with　constant　velocity　and　temperature　as　the　inlet　boundary　conditions　and　constant　pressure　as　the　outlet　boundary　condition　whilst　the　gauge　pressure　is　assumed　to　be　zero.　Results:　Compared　to　the　BCC　arrangement　mode,　the　streamline　under　the　FCC　arrangement　mode　is　more　complex,　the　flow　pressure　drop　is　larger,　the　fuel　ball　surface　temperature　distribution　is　more　uniform,　and　the　hot　spot　temperature　is　lower.　Under　the　FCC　arrangement　mode,　the　maximum　temperature　of　the　ball　center　is　1153　K,　the　total　pressure　drop　is　1323　Pa;　under　the　BCC　arrangement　mode,　the　maximum　temperature　of　the　ball　center　is　1155　K,　the　total　pressure　drop　is　574　Pa.　Conclusion:　The　streamlines　under　the　FCC　arrangement　mode　are　periodically　curved　and　the　streamlines　under　the　BCC　arrangement　mode　are　generally　straight.　Under　FCC　arrangement　mode,　the　surface　temperature　distribution　of　a　single　intermediate　fuel　ball　is　more　uniform　and　the　hot　spot　temperature　is　lower,　but　the　pressure　drop　from　the　bottom　of　the　fuel　ball　to　the　top　is　larger　than　that　of　BCC　arrangement　mode.