An experimental study was performed for the flow in a modeled hydraulic headbox of paper making machines. The turbulent boundary layer generated on the partition plate in the dispartion part and the wakes formed downstream of the plates were investigated by using the flow visualization technique of a smoke wire method and by hot-wire measurements. Those controls were explored for several kinds of test channels and the plates that differ in convergence and trailing edge shape, respectively. As a result, the rectification by contracting the channel is effective in making the distribution of the average velocity uniform and in attenuating and unifying the turbulence intensity. Furthermore, the uniformalization of the average velocity is high for the trailing edges of a tapered and a wavy shape, while the homogeneity of the turbulence intensity is excellent for the tapered edge.