Uniaxial　tensile　testing　is　the　most　effective　method　for　testing　ultra-high-performance　concrete　(UHPC)　damage　mechanism,　tensile　strength,　and　tensile　constitutive　relationship.　The　uniaxial　tensile　test　is　a　very　sensitive　and　difficult　test　to　conduct.　In　theory,　the　shape　effects　are　absent.　There　are　currently　no　testing　standards　available　that　define　the　test　conditions　and　specimen　geometry.　Then　unnotched　dog-bones　specimens　have　unique　advantages.　Due　to　the　typology　of　a　transition　region,　specimens　can　be　divided　into　the　arc-dog-bone,　the　trapezoid-dog-bone,　and　the　multiple-dog-bone　specimens.　Based　on　the　stress　analysis　of　the　specimen,　two　indexes　of　stress　distribution　were　put　forward　to　evaluate　the　specimens.　The　research　can　improve　the　success　rate　of　uniaxial　tensile　test　for　UHPC　by　designing　special　dog-bone　specimens.　Thusly,　the　effects　of　a　set　of　non-dimensional　geometric　parameters　on　the　stress　distribution　were　numerically　investigated.　A　total　of　275　dog-bones　specimens　were　analyzed　using　non-dimensional　parameters,　and　15　specimens　was　proposed　to　compare　the　three　types　of　dog-bone　specimens.　Based　on　the　stress　distribution　in　the　effective　test　area,　an　optimized　design　is　proposed　for　the　dog-bone　shape　to　improve　the　success　rate　of　the　uniaxial　tensile　test.　Twenty-four　dog-bone　specimens　were　tested　for　the　verification　of　the　optimized　dog-bone　shape,　the　success　rate　of　which　is　95.8%.　©　2018,　Engineering　Mechanics　Press.　All　right　reserved.