The synthesis and self-assembly studies of DNA/RNA-mimic artificial polymers have drawn extensive scientific attention since synthetic chemists can manipulate the functions of these modified nucleic acid molecules by varying their macromolecular backbone and nucleoside unit structures. In this paper, we report two types of modified nucleic acids with olefin bridges prepared by acyclic diene metathesis polymerization (ADMET). The 3'-OH and 5'-OH groups of deoxythymidine and deoxyadenosine analogue) monomers are functionalized with either two terminal allyl units or allyl and acryloyl units, respectively. The consequent ADMET approaches provide either regio-uncontrolled oligodeoxynucleosides with poor E/Z selectivity or well-defined oligodeoxynucleosides built in a highly ordered head-to-tail addition manner. These two different macromolecular structures markedly influence the self-assembly morphologies of the corresponding oligodeoxynucleosides, which show spherical and filamentous helix nanostructures, respectively.