Abstract: In order to further tap the remaining resources in the old region of Jilin Oilfield and make full use of the old well patterns, the tests were conducted to the old wells development by sidetrack horizontal well. Well Hongceping+24-022 was the first ?118 mm slim hole sidetrack horizontal well in Honggang Oilfield, which had long horizontal interval and was difficult to drill. Optimization of casing sidetracking, profile design and strong-inhibition drilling fluid system, ensured that the technical indicators such as the length of sidetrack openhole interval, the length of the horizontal interval, and average ROP, were all at an advanced level. Through analysis of difficulties in drilling and completion and presentation of field application, this paper fully summarizes the drilling and completion technique for ?118 mm sidetrack horizontal well with long horizontal interval, which is of guiding significance to the research and application of sidetrack horizontal wells.