Flashes with high frequency found in the traces of oscilloscope in the boundary-layer are a character of K-regime of transition from laminar to turbulence.These high frequency disturbances,called spikes,double,triple,etc downstream during each period.It is conclude that spikes are responsible for the final laminar-boundary-layer breakdown and flow randomization.The spike moves in a high speed after its formation and then acquires a rather conservation form which remains essentially unchanged further downstream.The spikes do not disperse but,on the contrary,gather,in narrow flashes and propagate steadily.The spikes,observed in the transition of K-regime,can be explained within the framework of the wave-resonant theory and considered as solitary waves.Nonlinear solitary-waves generated in the incompressible and their behaviors of randomization by external force are considered.Solitary-waves are pertinently modeled by the integral-different Benjamin-Ono equation.A travelling wave is chosen as a simple source in order to trace disturbance-pattern evolution as the amplitude of travelling wave increases.The solitary-waves,driven by guided travelling waves,travel downstream,with their wave-peak increasing abruptly during occurrence and disappearance of the saw tooth waves.Every increasing of wave-peak number corresponds to a solitary-wave energy jump.Randomization does not occur until the saw tooth waves no longer disappear.Saw tooth waves of small amplitudes lead to the randomization of solitary-waves in boundary-layer flows.