The　effects　of　biochar　on　Bermuda　grass　growth　and　mechanical　properties　of　vegetated　soil　were　investigated　in　this　study.　Six　groups　of　soil　column　tests　were　conducted,　including　two　degrees　of　compaction　(DOC)　(70%　and　90%)　and　two　types　of　biochar　content　(5%　and　10%　by　soil　dry　weight),　with　two　groups　of　bare　soil　serving　as　a　reference　(soil　used　in　the　test　was　classified　as　silty　sand　with　gravel,　i.e.,　SM).　It　was　found　that　biochar　increased　the　effective　cohesion　by　up　to　70%　and　slightly　enhanced　the　effective　internal　friction　angle　while　mitigating　the　detrimental　effects　of　wetting-drying　cycles,　with　the　effective　cohesion　and　friction　angle　retaining　up　to　73%　and　99%　of　their　initial　values,　respectively.　Root　biomass　initially　increased　and　then　decreased　as　biochar　content　increased,　particularly　at　a　low　degree　of　compaction　of　soil　(i.e.,　70%　DOC　was　two　times　that　of　90%　DOC).　The　effective　cohesion　of　intact　biochar-root-soil　initially　increased　up　to　23%　(at　the　biochar　content　of　5%,　90%　DOC)　and　then　decreased　as　biochar　content　increased,　regardless　of　DOC.　At　the　optimal　biochar　content　(5%),　the　effective　cohesion　and　internal　friction　angle　of　rooted　soil　were　1.4　and　1.1　times　greater　at　low　DOC　(70%).　For　the　remolded　biochar-root-soil　composite,　at　a　high　degree　of　compaction　(90%　DOC),　the　effective　cohesion　increased　with　the　increase　in　root　and　biochar　content.　For　a　given　root　content,　the　shear　strength　of　the　remolded　biochar-root-soil　mixture　was　higher　than　that　of　intact　biochar-root-soil　(i.e.,　the　shear　strength　of　intact　soil　at　5%　of　biochar　content　was　87%　of　remolded　soil),　suggesting　that　the　remolded　soil　mixture　overestimated　the　biochar-root-soil　strength.　Generally,　the　present　study　demonstrates　that　a　5%　biochar　addition　is　optimal　for　enhancing　plant　root　growth　and　soil　strength,　particularly　under　low　compaction.　Biochar　significantly　improves　the　mechanical　performance　of　root-soil　composites　and　mitigates　the　degradation　of　soil　strength　under　wetting-drying　cycles.