The invention discloses a three-dimensional shape sensing measurement method and device based on multi-core fibers, and belongs to the technical field of fiber shape sensing measurement. According tocentral wavelengths of fiber Bragg gratings before and after shape change of the multi-core fibers, maximum strain of the fiber gratings and curvatures and torsion angles of the positions where the cross sections of the fiber gratings are located are calculated, interpolation of the curvatures and the torsion angles is conducted on the multi-core fibers, three-dimensional shape reconstitution is conducted through a three-dimensional reconstruction algorithm, then displaying on a computer is conducted, and three-dimensional shape sensing measurement of the multi-core fibers is achieved. The measurement device comprises the computer, a fiber grating sensing analyzer and a multi-core fiber fan-in and fan-out module. A full-fiber structure is combined with the fiber grating measurement strain,by changing the distance between every two adjacent fiber gratings and the number of the fiber gratings, the measurement precision can be improved, the mounting error is eliminated through the adopted multi-core fibers, later maintenance, replacement and mounting are facilitated, and reliability is higher.