Abstract: The side-tracking wells in Shengli Oilfield commonly have Ø177.8 mm and Ø139.7 mm casing, so they face the problems of small annulus clearance and limited completion inner diameter. And especially the second-spud side tracking in buried-hill oil reservoirs is difficult, there is no steam injection technology to support the side-tracking wells in heavy oil reservoir and it is hard to realize mechanical sand control after the side tracking in sandstone oil reservoirs. To solve these problems, the side-tracking well reaming technology was selected, the design of large-bore liner completion scheme was optimized, and several support tools were developed, such as large-bore expandable hanger, pre-stressed earth anchor and rubber test joint. In addition, the support technologies were improved from the aspects of completion liner selection, slurry system optimization and casing central degree improvement. Thus, the large-bore liner completion technology for side-tracking well was formed. The field application results indicate that this technology can effectively solve the completion difficulties of side-tracking wells in special oil reservoirs, such as buried-hill oil reservoirs, heavy oil reservoirs and sandstone oil reservoirs, and its popularization prospect is promising.