Purpose　Kaolin　has　been　commonly　used　to　construct　the　hydraulic　barrier　of　landfill　cover.　Reduction　in　desiccation-induced　volume　shrinkage　of　compacted　kaolin　is　crucial　to　reduce　the　possibility　of　cracking　during　desiccation.　Nano-biochar　has　been　found　to　be　a　potential　soil　amendment.　The　present　study　aimed　to　investigate　the　effects　of　particle　size　of　nano-biochar　on　the　shrinkage　behavior　of　kaolin　amended　with　nano-biochar.　Materials　and　methods　The　kaolin　used　in　the　present　study　had　an　average　particle　size　of　14.5　mu　m　and　was　classified　as　high　plasticity　clay　(CH).　Two　nano-biochars　with　the　same　composition　but　different　average　particle　sizes　were　adopted,　including　NB-I　of　the　average　particle　size　of　20　nm　and　NB-II　of　300　nm.　Each　type　of　nano-biochar　was　mixed　with　kaolin　in　different　mass　percentages,　including　2%,　4%,　6%,　and　10%.The　shrinkage　properties　of　pure　kaolin　and　nano-biochar-amended　kaolin　were　determined　by　wax　method.　Afterwards,　the　microstructure　and　pore-size　distribution　of　the　specimens　were　analyzed　by　scanning　electron　microscopy　(SEM)　and　mercury　intrusion　porosimetry　(MIP),　respectively.　Results　and　discussion　The　optimal　content　of　NB-I　was　4%,　at　which　the　shrinkage　limit　of　kaolin　increased　by　66.7%　(i.e.,　volume　reduction　decreased　from　about　30%　to　10%),　due　to　more　micropores　(pore　diameter　D　＜　1000　nm)　but　less　macropores　(D　＞　10,000　nm)　after　nano-biochar　amendment　as　revealed　by　MIP　test.　Yet,　the　shrinkage　limit　of　the　kaolin　decreased　as　NB-I　content　further　increased,　when　NB-I　content　exceeded　4%.　It　was　due　to　more　macropores　at　higher　NC-I　content　(＞　4%)　caused　by　the　aggregation　of　the　fine　nano-particle.　In　contrast,　the　shrinkage　limit　of　kaolin　increased　at　a　reduced　rate　as　NC-II　content　increased,　which　was　consistent　with　the　more　micropores　observed　in　soil　specimens.　Conclusions　Nano-biochar　was　a　feasible　soil　amendment　to　enhance　the　shrinkage　limit　of　kaolin　and　hence　reduced　the　risk　of　desiccation-induced　cracks.　From　an　economic　and　practical　point　of　view,　4%　of　NB-I　was　suggested　to　reduce　volume　shrinkage　of　kaolin　and　crack　formation　during　desiccation.