The invention provides a method for preparing a metallographic specimen of an ultra-fine grain hot-rolled ribbed steel bar, which comprises the following steps of: limiting the particle size of a grinding wheel in a flat grinding machine in the step (3) to be 80 meshes, adjusting to use 320-mesh abrasive paper in the step (4), and carrying out multiple combined tests on the abrasive paper in the step (4) and other abrasive paper with various meshes, preferably 800-mesh abrasive paper as the step (5), so as to obtain the metallographic specimen of the ultra-fine grain hot-rolled ribbed steel bar. After improvement, the method only comprises seven steps, two steps are omitted compared with a traditional sample preparation method, grinding and polishing operation can be completed within two minutes by using the method, about three minutes are saved compared with the traditional sample preparation method, the operation efficiency of metallographic sample preparation is greatly improved, meanwhile, an inspection surface is free of illusion, and the method is suitable for large-scale popularization and application. The sample forming rate can reach 100%; the sample preparation steps are simplified, the time spent on grinding and polishing is shortened, the sample preparation efficiency and effect are improved, the labor intensity of workers is reduced, and meanwhile it is guaranteed that the sample preparation quality reaches the standard.