Abstract: Well Shu 125-H3, deployed in the Shu 125 Block in the Shuguang low buried hill, western Liaohe depression, is a technically special well to control more reserves by using complicated multilateral well technique. It is the first multilateral well sidetracked through ?193.7 mm casing hole. Operations of Well Shu 125-H3 were challenged by complicated well structure, restricted well site,large well depth, long horizontal section and upwarding trajectory. Through optimizations of casing program, casing hole position and hole trajectory, the well structure was optimized effectively and the drilling investment was reduced. Technical difficulties in field operations were addressed by virtue of high-pressure whipstock seat, optimal drilling tools, optimized drilling mode, immediate reaming,drifting with highly-stiff tools, and bend-conductor re-entry. The successful drilling and completion of Well Shu 125-H3 recommends a new casing program of multilateral well to reduce drilling cost effectively and increase single-well sweeping coverage.