As for wall jet, the pioneering investigation was done by Glauert and the appealing work has been performed by Schwartz and Cosart and Tsuchiya. In these investigation, smooth wall was chosen as the subject, and analysis was done assuming the similarity of the velocity distribution. On a practical case of hydraulic engineering, it may be to consider that the wall was rough hydraulically. In such a case, the boundary layer growth is closely related to the scale of roughness. Therefore, with the above assumption, a theory of this problem can't be developed. As all studies show that the law of the wall is not applciable to the turbulent wall jet in the form that was obtained by experimentation in turbulent boundary layer, and turbulent pipe and channel flows. But we can't give a clear physical interpretation for it. In this paper the author describe an experimental study of the characteristics of the plane turbulent wall jet issuing along smooth or rough boundary, and examine the distribution of the turbulent shear stress and the eddy viscous coefficient using the equation of motion applied the boundary layer approximation and the measured velocity distribution, and analyzed the boundary layer using these results. In consideration on the law of the wall, the boundary layer are divided into two regions, the first region is called the outer layer occupies the major portion of the flow, where the turbulence of the main flow plays an important role, second region is the wall region consists of viscous sublayer and turbulent sublayer, where the flow are defined by the property of the wall. The derived velocity law, in particular case, coincide with Parandtl-Karman's logarithmic distribution, and contain the eddy viscosity coefficient of the main flow in position of parameter.