The dynamic evolution of the mode-locked regenerative amplifier based on single mode fiber, which is also called pulse-based start-up dissipative soliton mode-locked laser, is numerically simulated, and the evolutions of the pulse energy, pulse duration, and spectral bandwidth versus the cycling number of the incident pulse in the cavity are analyzed. By using an electro-optic modulator in the cavity, the input pulses can be successfully injected into the cavity for circulation. With the demonstration of the timing sequence of the modulator, the laser runs steadily for 13 roundtrip. Meanwhile, when the circulation roundtrip is fixed at 2, the influence of the pump power on the output spectrum is investigated. The final output laser pulse has a spectral bandwidth of 60 nm and single-shot pulse energy of 20 nJ. Besides, the reason that the output pulse energy is limited in the mode-locked regenerative amplifier based on a single mode fiber is also analyzed.