The evolution of picosecond seed pulses in the normal dispersion-flattened fiber to generate supercontinuum (SC) is investigated. The appearance of wave breaking during the process and the effect of the revealed four-wave mixing on the char acteristics of SC are also analyzed. The research indicates that the broadening of the pulse spectrum in the initial stage is dominated by the self-phase modulation. Afterwards, self-phase modulation is impaired while four-wave mixing is enhanced due to energy in the inner spectrum region being transferred continuously to the outside wings by dispersion, and the pulse spectrum further broadens remarkably. The characteristic of SC noise manifests the dynamic responses of typical SC spectral structures to the seed pulse amplitude noise that are closely related to the evolution.