Abstract: The three-section large-bore casing program of deep coalbed methane (CBM) horizontal wells in the Zimi Block of the eastern Ordos Basin suffers from problems such as low drilling efficiency and long downhole treatment cycles for issues like lost circulation and well collapse, making it difficult to meet the needs of low-cost and efficient CBM development. To this end, by analyzing regional geological characteristics, drilling engineering challenges, and the problems in the three-section large-bore casing program, a “conductor pipe+deep surface layer” two-section small-bore “slimmed-down” casing program was innovatively designed. Key technologies such as the selection of efficient speed-up tools for “one-trip drilling”, optimization of drilling hydraulic parameters, three-dimensional horizontal well trajectory control, drilling fluid systems with strong inhibition, strong plugging, and low filtration, and optimization of segmented measures were studied to develop deep CBM horizontal well drilling technology in the Zimi Block. In field trials, this technology was applied to the drilling of four wells, with an average well depth of 3 902 m and an average rate of penetration of 13.24 m/h. The single-well complication treatment cycle was reduced from 225.00 h to 32.75 h, the drilling cycle was shortened from 82.54 d to 27.12 d, and drilling costs were decreased by 34.53%, thus achieving the technical goal of “separate treatment of collapse and leakage”, and solving the problems of low drilling efficiency and frequent downhole complications in deep CBM development. The proposed technology could provide technical support for the low-cost, large-scale, and efficient development of deep CBM in the gas fields of the eastern Ordos Basin.