To investigate the physical characteristics of buckwheat (Fagopyrum esculentum Moench) seeds, ten physical characteristics of five buckwheat cultivars were researched on their seeds, shells and kernels. The results showed that buckwheat seed moisture percentage was 11.6%-13.4% and the size of more than 90% of buckwheat seed grains was 3.8-5.0 mm. The color values of L^*, a^* and b^* in kernels were about 1.8 times, 1.7 times and 2.6 times higher than those in seeds, respectively. And then the thousand grain weight of buckwheat seeds and the volume weights of seeds and kernels were measured to be 27.1-37.2 g, 578-698 kg/m³, and 699-795 kg/m³ respectively. Moreover, specific weight of seeds, shells and kernels were also valuated to be about 1.11 g/cm³, 0.61 g/cm³ and 1.13 g/cm³, and the weight percentage of shell and kernel accounted for seeds was 13.8%-19.2% and 80.8%-86.2% respectively. In addition, the thickness of seed shells and the gaps between shells and kernels were found to be about 0.18 and 0.09-0.12 mm, and the. seed kernel hardness was measure to be 1.07-1.26 kg. Therefor, different buckwheat species showed relatively large differences in their seed moisture percentage, thousand grain weight, volume weight of seed and kernel, weight percentage of shell and kernel accounted for seeds, clearance between shell and kernel of seeds, and seed kernel hardness. Consequently, the commonality and specificity in seed physical characteristics among the different species might provide us some valuable information for the researches of the techniques and the adjustment of production process technologies in buckwheat hulling.