The　negative　thermal　expansion　(NTE)　properties　of　the　antiperovskite　manganese　nitrides　with　micron-scale,　submicron-scale　and　nanometer-scale　microstructures,　respectively,　were　investigated　using　the　Mn3Cu0.5Ge0.5N　composition　as　an　example.　It　was　discovered　that　the　NTE　start　temperature,　NTE　operation　temperature　range　and　coefficient　of　NTE　change　obviously　in　a　wide　range　with　decreasing　the　grain　size　level　of　the　microstructure.　The　mechanisms　for　the　broadening　of　the　NTE　operation　temperature　range　and　the　decrease　in　the　absolute　value　of　NTE　coefficient　were　proposed　based　on　the　grain-size-dependence　of　the　frustrated　magnetic　interactions　and　magnetic　ordering.　The　present　study　indicates　that　the　NTE　properties　of　the　antiperovskite　manganese　nitrides　can　be　tailored　by　the　control　of　the　microstructure　scale.