The invention discloses a low-bending-loss microstructure optical fiber which is composed of matrix materials, a round high-refractive-index fiber core, round low-refractive-index dielectric cylinders distributed around the fiber core and round air holes distributed outside the low-refractive-index dielectric cylinders. The distances between the centers of the low-refractive-index dielectric cylinders and the center of the fiber core are the same respectively. The distances between the centers of the air holes and the center of the fiber core are the same respectively. The air holes are arranged into the optical fiber, and bending loss of the optical fiber is effectively reduced by aid of the low-refractive-index air holes. The low-refractive-index dielectric cylinders are arranged around the fiber core so that low double refraction and low transmission loss of the optical fiber and similarity of the mode field of single mode fibers are ensured. A fundamental mode of the microstructure optical fiber can still have low bending loss when the bending radius is 5mm, optical fiber production accuracy requirements are reduced by aid of the introduced low-refractive-index dielectric cylinders, and product yield is improved.