A modified ring fiber by introducing a high refractive index layer is proposed. With the effect of mode reorganization, index differences between the orbital angular momentum (OAM) modes are enlarged, thereby reducing the degeneracy among OAM modes. Parameters of the modified ring fiber are designed properly by numerical simulations, and modal index difference of about 10-3 is achieved, which effectively minimizes the coupling between OAM modes and thus improves the transmission property of ring fiber.