A theoretical model of the eccentric core fiber was established based on traditional optical transmission theory. By using conformal mapping, the asymmetric three-layer structure of the eccentric core fiber was converted into a three-layer structure of coaxial symmetry. Characteristic equation about propagation constant was obtained. Bending loss formula of eccentric fiber was given. The relationship between bending loss and bending radius of the eccentric fiber was analyzed by simulation. When the bending radius reaches 3 mm, the bending loss is almost zero. Meanwhile, the relationship between bending loss and eccentricity distance change was obtained. Optical model of eccentric fiber bending was established by using BeamPROP module in Rsoft software. Mode field distribution in the curved eccentric core fiber was simulated. The simulation result shows that bending loss of the eccentric optical fiber in the same direction as that of the core deflection center axis is smaller than that of the opposite direction.