The invention discloses a long and big pile foundation classified steel casing pipe whole-pile advanced water isolation and support drilling hole forming method, and belongs to the technical field of drilled pile foundation drilling construction. The problem that drilling is difficult when a drilled pile foundation penetrates deep silt body soft soil and the high confined water complex environment can be solved. The method comprises the following steps that a casing pipe drilling machine is moved and aligned; rotation and downward pressing are conducted, drilling is conducted into a first-level steel casing pipe connected with a blade foot, slag taking equipment is used for slag taking, drilling and hole forming are conducted, rotation and downward pressing are conducted, drilling is conducted into a second-level steel casing pipe connected with a blade foot, the slag taking equipment is used for slag taking, and drilling and hole forming are conducted to the pile bottom. The technology is simple, environment-friendly, efficient and convenient to operate.