Early　onset　scoliosis　(EOS)　is　a　type　of　spine　deformity　that　presents　before　10　years　of　age.　The　biomechanical　properties　in　scoliosis　have　been　found　to　be　different,　especially　in　the　case　of　the　concave　and　convex　paravertebral　muscles.　Based　on　this　fact,　a　novel　three-dimensional　(3D)　printed　patient-specific　asymmetric　stiffness　brace　design　method　is　proposed　in　this　paper,　aiming　to　provide　asymmetric　stiffness　to　match　＂imbalanced＂　biomechanical　properties　of　the　concave　and　convex　paravertebral　muscles,　respectively,　and　treat　EOS　by　applying　the　block-structure　brace.　A　3D　computer　aided　design　draft　model　of　the　brace　contour　was　implemented　from　3D　scanning.　The　asymmetric　stiffness　block-structure　brace　was　designed　in　Rhinoceros　and　the　finite　element　(FE)　model　was　imported　into　abaqus.　FE　simulation　was　employed　to　study　the　mechanical　characteristics　of　the　brace,　which　provided　a　quantitative　index　for　the　imbalanced　property　of　brace　stiffness.　The　results　of　the　FE　simulation　showed　that　the　stiffnesses　of　the　concave　and　convex　sides　were　145.88　N/mm　and　35.95　N/mm,　respectively.　The　block-structure　brace　was　fabricated　using　3D　printing.　Asymmetric　stiffness　was　evaluated　by　corrective　force　measurements,　which　were　obtained　from　a　thin-film　pressure　sensor　equipped　on　the　brace.　The　patient-specific　asymmetric　stiffness　brace　was　applied　to　clinical　practice　in　a　one-year-old　EOS　patient.　A　novel　low-cost　3D　printed　brace　design　method　for　EOS　was　proposed　in　this　study　that　could　potentially　be　useful　in　patient　treatment　acceptance.