It is crucial but challengeable that the generation of optical exact by synchronized seed pulses both for the main amplifier chain and for the pump-laser chain of an optical parametric chirped pulse amplification system, which are tried to be developed by the soliton mechanism. Detailed numerical simulation of the soliton propagation mechanism are accomplished. So the evolutions of solitons in time-domain and frequency-domain as well as the reciprocity characteristic with other nonlinear effects are clarified. Experiments are carried out, for validating the method of using soliton mechanism to generate ultra-broad band tunable ultra-short laser pulses. Forming, breaking up and self-frequency shift of a soliton are observed. The favorable tunablenesses of the wavelength between the visible and the near-infrared regions are exhibited. All these experimental results are well consistent with the theoretical analyses.