Due　to　high　programmability　and　good　biocompatibility,　DNA　has　been　recognized　as　a　powerful　building　block　for　engineering　of　sophisticated　nanostructures　for　different　purposes.　Herein,　we　present　the　first　example　of　a　bead-string-shaped　DNA　nanowire　(BS-nanow)　with　long-range　structural　order　for　in　vivo　bioimaging　and　targeted　drug　delivery.　BS-nanow　is　assembled　from　DNA　tetrahedron　units　with　precise　nanometer-scale　spatial　control,　capable　of　accommodating　chemotherapeutic　agents　with　high　payload　capacity　(1204　binding　sites)　as　well　as　possessing　a　60-fold　enhanced　binding　affinity　for　target　cells.　Confocal　fluorescence　imaging　and　in　vivo　experiments　on　CEM　subcutaneous　tumor-bearing　mice　show　that　specific　bioimaging　of　living　cells　and　even　systemic　delivery　of　drugs　into　internal　tumor　organs　and　tissues　were　accomplished,　thereby　achieving　an　efficient　inhibition　of　tumor　growth　in　the　xenograft　model　without　systemic　toxicity.　BS-nanow＇s　show　potential　in　vivo　applications　in　accurate　diagnosis　and　targeted　therapy　for　human　cancer.