Based on the NLS equation and variational method, the evolution equations for the parameters of the super-Gaussian pulse in single-mode optical fibers are deduced. Then three restricted relations between amplitude and width, frequency and chirp, width and chirp are derived. Analytical solution about the width of pulse evolves on the propagation distance is obtained. By using Runge-Kutta algorithm, the influences of the initial chirps and the degree of the pulse’s edge sharpness on the pulse width are described. The result indicates that initial chirps and the degree of the pulse’s edge sharpness have effect on amplitude, width, chirp and phase, and super-pulse has a chirp in the process of transmission, but the pulse centre equivalent frequency maintains a constant.