The invention relates to a multi-scale sample mounting and positioning mechanism. The multi-scale sample mounting and positioning mechanism comprises a framework platform, a sample limiting seat, a sample loading plate, L-shaped plates, a sample mounting plate, tangential guide rails, a trolley, a second-level telescopic oil cylinder, a lifting hydraulic cylinder, a sample conveying frame and a support rod, wherein the L-shaped plates are respectively mounted on the upper and lower part of a sample in an opposite angle manner, the sample is mounted on the sample mounting plate and is limited by the sample limiting seat, the tangential guide rails are mounted on the trolley, and the sample mounting plate is mounted on the tangential guide rails; the sample conveying frame is mounted on one side of the framework platform, the second-level telescopic oil cylinder is mounted in the framework platform, a support head is mounted on a piston rod of the second-level telescopic oil cylinder, and the support rod is mounted on the support head; the trolley moves on limiting grooves in two sides of the sample conveying frame, the upper rod is connected with the trolley, and an action end of the lifting hydraulic cylinder is located below the trolley and the sample mounting plate. By virtue of mechanized operation, the multi-scale sample mounting and positioning mechanism is relatively high in working efficiency, and the labor intensity is reduced.