We present a novel and robust design for a photonic crystal fiber with flattened dispersion, a highly nonlinear coefficient, and low confinement loss for its dual concentric core structure. The proposed fiber has a modest number of design parameters. Analysis results show that the proposed eight-ring photonic crystal fiber is obtained with a nonlinear coefficient greater than $33{\mathrm{W}}^{-1}{\mathrm{km}}^{-1}$ and a near-zero dispersion slope of $-7.828\times {10}^{-4}\mathrm{ps}/{\mathrm{nm}}^2/\mathrm{km}$ at $1550\mathrm{nm}$ . Ultraflat dispersion with a value between $-1.380$ and $+0.9860\mathrm{ps}/\mathrm{nm}/\mathrm{km}$ and a superlow-order confinement loss of ${10}^{-4}\mathrm{dB}/\mathrm{km}$ are simultaneously obtained ranging from 1400 to $1625\mathrm{nm}$ . For practical fabrication, the influence of random imperfections of airhole diameters on dispersion and nonlinearity is discussed to verify the robustness of our design.