Cobalt　nanowires　with　different　shapes　and　sizes　were　synthesized　by　reduction　of　carboxylate　salts　of　CoII　in　1,　2-butanediol　using　a　solvothermal　chemical　process.　The　well-crystallized　Co　nanowires　with　hexagonal　close-packed　(hcp)　phase　are　observed　and　the　(002)　crystalline　direction　is　along　the　long　axis　of　nanowires.　The　morphology　control　is　strongly　dependent　on　the　reaction　parameters.　By　varying　the　amount　of　capping　agent　in　proper　ranges,　the　effect　of　reaction　parameters　on　controlling　the　size　and　shape　of　Co　nanowires　is　demonstrated.　With　the　amount　of　capping　agent　increasing,　the　aspect　ratio　of　Co　nanowires　increases　remarkably.　However,　the　magnetic　measurement　of　cobalt　nanowires　shows　that　the　coercivity　of　the　Co　nanocrystals　does　not　increase　with　the　increase　in　aspect　ratio　monotonously,　which　suggests　that　the　tip　shape　and　microstructure　also　play　an　important　role　in　the　magnetization　reversal　process　of　the　Co　nanocrystals,　and　the　aspect　ratio　plays　a　much　less　role　as　the　ratio　value　exceeds　11.　To　further　understand　the　effect　of　size　on　the　magnetic　properties　in　the　Co　nanowires,　micromagnetic　simulations　were　performed,　which　confirms　that　the　magnetic　properties　are　barely　affected　by　the　aspect　ratio　larger　than　10.　The　highest　coercivity　of　624　kA·m−1　is　obtained　for　ellipsoid　nanowires　with　a　mean　length　of　200 nm,　which　also　displays　a　strong　magnetic　anisotropy.　As　a　result,　the　highest　energy　product　of　the　wires　reaches　248 kJ·m−3.　©　2018,　The　Nonferrous　Metals　Society　of　China　and　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature.