Abstract: Because of the Yuanba block formation pressure system is complex, with high temperature and high pressure, marine strata containing H2S, difficulty in selecting casing program existed in Guangyuan ultra deep horizontal well with narrow range of selection on the drill bit sizes and casing sizes. In the paper, Analysis of four kinds of well structure design method and the existing main problem are made, the optimized design plan is put forward, which avoided the differential pressure sticking caused by the casing program and laid the foundation for optimal and fast drilling.