In order to analyze influnce of laser pulse width on backward detection of long-distance wake bubbles, firstly, a simulated model is built to analyze the time-domain characteristics of the laser pulse′s backscttering signal underwater with Monte Carlo method based on Fournier Forand volume scattering function. Using this model, the variation of laser pulse′s backscttering signal by long-distance ship wake bubbles underwater with the width of initial laser pulse is studied. The result shows that, with the increase of the width of laser pulse, the outline of scattering signal by water and echo signal by wake bubbleds in backscattering signal become vague. When the width increases to a certain size, the echo signal cannot be distinguished from backscattering signal. In addition, with the decrease of the scattering intensity of bubbles or the distance between bubbles and detector, the variation becomes more evident. Finally, according to analysis results, a method is presented to extract the echo signal by wake bubbles based on inverse convolution.