Abstract: The U form aqueduct of reinforced concrete, has been commonly adopted in our country since 1960' s. The choice of the optimal geometric parameters in the cross section cannot be well solved all the while in designing. For the U form agueduct of reinforced concrete with simply supported and same thickness, through a series of optimal calculations in combination with the all sorts of the modulus of discharge K and the calculating span L, some utility regularities for reasonable choicing the geometric parameters in cross section of the U form aqueduct has been obtained. This article has simply introduced these results and regularities.