The utility model discloses a sensor based on single mode little core single mode of draing single mode fiber structure, include: a single mode fiber, draw little core single mode, its input and a single mode fiber's output butt fusion, draw little core single mode fiber's surface adhesion giant magnetostriction materials layer, the 2nd single mode fiber, its input with draw little core single mode fiber's output butt fusion. In the carrier roller device, light when superradiance LED source sends transmits in a single mode fiber, the entering is drawd to form among the little core single mode fiber and is interfered, the light of part wavelength is wherein forming the trough, continue to transmit in then getting into the 2nd single mode fiber, thereby lead to giant magnetostriction materials emergence micro -deformation and waveguide refracting index to influence the change of waveguide interference condition in magnetic field environment when having the little core single mode fiberof draing of giant magnetostriction materials layer, lead to the skew of resonance wavelength, offset according to resonance wavelength, obtain the change volume in magnetic field.