With hydraulic model, the hydraulic characteristics of the stilling basin with drop sill in the trapezoidal drainage open channel of a Indonesia power plant are experimental analysis, and the scales of stilling basin are also optimized. The test results showed that the width of head fall is bigger than bottom width of trapezoidal open channel, in order to improve effect of energy dissipation, and avoiding jet flow fling straight the slope of stilling basin, the bottom width of stilling basin should be equal or greater than the width of head fall, meanwhile. Meanwhile, broaden manner to trapezoidal stilling basin can also influence the dissipation. The broaden manner of optimization scheme proposed in the test can effective improve the energy dissipation, it provided the technical support for engineering design. The test results can also be taken as a reference for the other similar projects.