The invention provides a few-mode fiber which comprises a fiber core and cladding. The fiber core comprises an inner fiber core body and an outer fiber core body encircling the inner fiber core body. The cladding comprises an adjacent core low-refractive-index layer encircling the outer fiber core body, a microstructure defect area encircling the adjacent core low-refractive-index layer, an adjacent encircling low-refractive-index layer encircling the microstructure defect area and an outer encircling layer encircling the adjacent encircling low-refractive-index layer. The microstructure defect area is composed of high-refractive-index mode filter layers and low-refractive-index mode filter layers, wherein the high-refractive-index mode filter layers and the low-refractive-index mode filter layers are arranged alternately. The fiber is a non-single-mode fiber under the straight waveguide state; after the fiber is properly bent, strong coupling occurs between a high-order mode of the fiber and a defect mode of the microstructure defect area, so that the purpose of filtering out the high-order mode of the fiber is achieved, and single-mode transmission is achieved.