Abstract: Slim liner cementing in ultra-deep wells with narrow annulus in the No.1 District of the Shunbei Block faces a series of technical challenges such as weak cement sheath, high displacement pumping pressure, low displacement efficiency, high bottomhole temperature and the development of high-pressure brine layer, which compromises the cementing quality. In order to solve those problems, on the basis of summarizing the previous operation experiences, small liner cementing technology for ultra-deep wells with narrow annulus in the No. 1 District of the Shunbei Block was formed by improving wellbore preparation technologies, optimizing the high temperature/gas channeling-proof elastic toughness cement slurry system, conducting cement stone sealing integrity research and carrying out cementing rheology design and stable-killing gas channeling-proof optimization. It has been applied in 3 wells in this area with good cementing quality. The subsequent operations were free from water intrusion, ensuring the long-term sealing of section with a narrow annulus. This cementing technology can not only effectively solve the cementing problems of this block, but also effectively ensure the safe and efficient development of the block.