The invention relates to the technical field of metallographic cutting, in particular to a clamping and positioning device for cutting a metallographic sample and a clamping and positioning method thereof. The clamping and positioning device comprises a support mechanism and a clamp mechanism, wherein the support mechanism comprises a support base, a support, a sliding sleeve, a sliding sleeve adjusting and locking assembly, a sliding block and a locking base, and the clamp mechanism comprises a supporting block, an upper clamping block, a lower clamping block, a jacking screw, two supportingguide rods and a plurality of pressing screws. When a metallographic cutting machine is used for cutting the special-shaped sample, the clamping and positioning device can effectively clamp and fix the special-shaped sample, the sample is firmly locked, thus loosening or falling in the cutting process is avoided, the sample cutting is precise without damaging equipment, the relative positions of the sample and the cutting knife can be conveniently and flexibly adjusted, and precise positioning is realized, so that the required sample part can be cut, the cutting requirement is met without frequently replacing a clamp, the labor intensity is reduced, the cutting efficiency is improved, and the equipment is effectively maintained.