The time-stretch dispersion Fourier transform (TS-DFT) technology promotes the study of transient phenomena in mode-locked lasers and is of great significance for revealing the dissipative dynamics in complex systems. In this paper, we first introduce the fundamental principles of TS-DFT technology and its key issues in data acquisition and data processing. Then we review the applications of TS-DFT technology in the study of various ultrafast phenomena in passively mode-locked fiber lasers, such as noise-like pulse and rogue wave, soliton explosion, soliton bound state, mode-locked self-starting, and vector solitons.