In regard of the problems of easy collapse of oil shale, difficulty in sliding of PDC drill, and low rate of penetration in deflecting segment, due to long length and steep well deflection of Chang 7 oil shale segment, low load bearing capacity of Chang 4+5 stratum, and failure of drilling fluid density to meet the required density for balancing collapse pressure of oil shale during drilling for horizontal wells of Chang 8 target stratum of Huang 36 Well Area, density is raised by lowering displacement from pure plugging and leakage prevention, and collapse pressure of oil shale segment is improved by lowering alternating stress of oil shale and controlling well deflection of oil shale segment. In addition, the method of deflecting by roller bit is adopted to lower collapse probability and effectively improve rate of penetration. The method effectively solves the problem of narrow-density windows, facilitates guaranteeing drilling safety, improves construction efficiency and lowers drilling cost.