The supercontinuum (SC) generation (SCG) based on the active nonlinear fiber has attracted much attention due to its advantages in the energy amplification and spectral broadening of the output pulses. The active step-index single-mode fiber is proposed for the SCG. A flat normal-dispersion profile ranging from 1 240 nm to 2 550 nm can be obtained by tuning the germanium (Ge) concentration and core size, where the values of the dispersion slope are between -0.01 ps/nm²/km and 0.05 ps/nm²/km. Furthermore, the output pulse from the 5 m Er-doped normal-dispersion fiber (NDF) with g₀=9 ^-1 has a peak power of 2.8 kW and a 20 dB spectral bandwidth of 507 nm ranging from 1 262 nm to 1 769 nm by using the 1 550 nm and 1 ps Gaussian pulse with a peak power of 10 kW as the pumping source.