Sanjiang basin, with the Mesozoic marine and land sea interaction deposition and after the transformation of multiple tectonic movements, its covering layer is thick soft-plastic formation. According to the stratigraphic characteristics of Sanjiang basin and drilling difficulties in drilling construction, the study was made on drilling methods, borehole design, flush fluid and process measures, the technical measures suitable for highly straight drilling were carried out without casing in thick overburden strata of soft plastic formation in Sanjiang basin, and the drilling difficulties were solved in the practice with good economic effect.