A folded cavity mode-locked system has been employed by using the core device SESAM ( semiconduc- tor saturable absorption mirror) for related experiments. The 1 064 nm picosecond ultrafast pulse has been expected to be obtained in experiments. Its characteristics based on waveform and power have been analyzed. At the same time ,the influence of pump power and cavity length have also been explored. Finally ,the mode-locked pulse waveform with repetition rate of 92. 25 MHz has been obtained. It is shown that with a certain cavity length ,the mode-locked pulse will not start if the pump power is insufficient. If the pump power is too high ,Q-switched instability and multi-pulse phenomena will be observed. Within the range of pump power that leads to mode-locked effect ,the average power of the mode-locked pulse is positively corrected with it. When the pump power is constant ,the mode-locked pulse wave- form is very sensitive to the change of the length of the folded cavity. The change of the cavity length of less than 1mm will make the waveform jitter greatly ,and the stable comb wave will appear only in a very small cavity length range.