The invention relates to a bar piece supporting device designed according to the Hopkinson test conditions. The bar piece supporting device mainly consists of adjusting parts, locking nuts, a support frame, an adapter block, a slide block and bar pieces, and is mainly and structurally characterized in that the three adjusting parts capable of freely extending and contracting along shaft lines of the adjusting parts are uniformly distributed on an annular framework, the center space size and the position of the supporting device are adjusted, and further, the center bar pieces are supported, and the axial motion of the bar pieces is limited; the bar pieces are supported by bearings at the end parts of the adjusting parts; and meanwhile, the free axial motion of the bar pieces is realized by utilizing the rotation of the bearings. The bar piece supporting device is formed by the simple parts and has the advantages of simplicity, reliability, small size, large adjustable scope, bearing rolling friction adopted in the bar pieces and small resistance, and the degree of freedom of the bar pieces and the rotation motion along shafts can be effectively limited; meanwhile, the axial motion of the bar pieces can not be influenced basically; and as the adjusting scope of the supporting device self is large, the bar piece supporting device can adapt to the bar pieces of which the diameters are within a certain scope.