A sample gauge length and length after fracture measuring device includes a worktable, a first sliding table support and a second sliding table support, a control and length display, a spiral micrometer head, a scriber, a sample, etc. The reading device using the spiral micrometer head to directly measure the gauge length and the length after fracture has a detection accuracy of ±0.01 mm, which is superior to the requirement of ±0.05 mm in GB/T228 Metallic Materials Tensile Testing at Ambient Temperature.