The embodiments of the invention provide a multi-core fiber grating, a fiber sensor, and a manufacturing method of the multi-core fiber grating, and relate to the technical field of fiber sensors. Themulti-core fiber grating comprises a plurality of fiber cores and a cladding, wherein the cladding is wrapped by the plurality of fiber cores; the target fiber core among the plurality of fiber coresis arranged at the center of the cladding; and when the plurality of fiber cores generate bending strain, the wavelength of each fiber core is provided with different strain response rules so as to measure the amplitude and the direction of the bending strain generated from the plurality of fiber cores. The multi-core fiber grating is simple in structure.