We present a numerical study of the effective mode dispersion characteristics modification of nonlinear photonic crystal fibers by their twisting effects. A photonic crystal fiber based on fused silica glass, with eight rings of air holes ordered in a hexagonal lattice, is proposed. The guiding properties in terms of dispersion, confinement loss, and mode area of the fundamental mode are studied numerically. As a result, although reducing the helix period makes dispersion less flat, the bandwidth of the ultra-flat dispersion region increases. In addition, changing the helix period can move the dispersion from an anomalous to a normal region. The influence of the helix period on the supercontinuum generation of the fiber was demonstrated.