Abstract: The nickel plate thickness of the nickel coated copper wire was measured by metallographic method. The uncertainty which influencing the plate thickness measuring results was analyzed from the aspects of repeatability of experiment, verticality of inlaying sample and measuring accuracy of optical microscope, each uncertainty components were calculated and synthesized, and the uncertainty report for nickel plate thickness measurement were given at last. The results show that the measured nickel plate thickness of the nickel coated copper wire was 16.57 μm, with the expanded uncertainty U=1.68 μm and the coverage factor k=2.