Based on the nonlinear Schrdinger equation, the variational method is used to derive the evolution equations for the parameters of the super-Gaussian pulse in fibers with slowly decreasing dispersion. The effect of initial chirp on the super-Gaussian pulse is discussed. Then three restricted relations between amplitude and width, frequency and chirp, width and chirp are derived. Analytical solution about the evolution of pulse width versus propagation distance is obtained. By using Runge-Kutta algorithm, the influence of the initial chirps and the degree of the pulse’s edge sharpness on the pulse width is described. The results show that initial chirps, dispersion decreasing and the degree of the pulse’s edge sharpness have direct influence on amplitude, width, chirp and phase. The degree of the pulse’s edge sharpness has no effect on pulse central position, and the super-Gaussian pulse in the process of transmission can cause chirps, but the equivalent frequency keeps constant.