The article divides the whole section into two sections. One is arcuate section. The other is seepage section. Water velocity distribution in circular section of pipe has been studied for a long time, and advanced theories were achieved. Based on fore theory and some tentatives, theory about distribution of water velocity in pipe of arcuate section is researched. Research of seepage section is based on seeping theory. Many experiments proved that the theory and program of this article are correct.