Ni-Co　alloys　with　Co　content　varying　from　2.4%　to　59.3%　were　prepared　by　pulse　electrodeposition　nanocrystalline.　The　microstructures　of　the　nanocrystalline　Ni-Co　alloys　were　characterized　by　XRD　and　TEM.　The　analysis　of　XRD　indicates　that　nanocrystalline　Ni-Co　alloys　are　all　face-centered　cubic　structure,　single-phase　solid　solution　with　an　average　grain　size　in　the　range　of　11-24　nm,　and　the　average　grain　size　decreases　with　increasing　Co　content.　The　grain　size　observed　in　the　TEM　structures　of　as-deposited　Ni-Co　alloys　is　consistent　with　that　measured　by　XRD.　For　nanocrystalline　Ni-Co　alloys,　the　ultimate　tension　strength　is　in　the　range　of　1300-1650　MPa　and　the　elongation　to　failure　is　in　the　range　of　10.5%-14.5%.　Both　the　ultimate　tension　strength　and　the　elongation　to　failure　increase　with　increasing　Co　content.　With　increasing　Co　content,　the　grain　growth　in　the　process　of　tension　deformation　is　gradually　suppressed　leading　to　improved　work　hardening　rate　and　delayed　plasticity　instability,　which　aids　to　obtain　enhanced　ductility.