In a homotropic nematic cell, a solitary-like director wave is excited by a mechanical method. A series of photographs of the wave propagation process are obtained. When white light is used, we noticed the propagation of some dark lines along the cell, and we got the plot of the positions and velocities of the dark lines vs time. According to the results obtained from the interference patterns of focused polarized light, it was shown that the dark lines correspond to a perpendicular alignment state of the director, in addition, the scattered light by liquid crystal is observed clearly on the two sides of dark lines. From the wave propagation process recorded by monochromatic light, and by using an one dimension postulat, we calculated the spatial distribution of the directors. Finally, some discussion on the physical model of the director wave is given.