The invention provides a novel rotary excavating hole forming method for a pebble layer. The novel rotary excavating hole forming method for the pebble layer comprises the following steps that firstly, rotary excavating hole drilling is carried out, and then a first section of pile casing is spun into a drilling hole; then rotary excavating hole drilling is carried out downwards continuously, a second section of pile casing is coaxially connected with the first section of pile casing to form an integral pile casing, and continue spinning is carried out; then rotary excavating hole drilling iscarried out downwards continuously, a third section of pile casing is coaxially connected with the first two pile casings into a whole, and continue spinning is carried out; by analogy, the pile casings are spun while drilling down; the first section of pile casing is always located at the bottom, the top surface of the uppermost section of pile casing is always located at an orifice of the drilling hole, and the bottom of the upper section of pile casing and the top of the next section of pile casing are both fixedly connected in the drilling hole. According to the novel rotary excavating hole forming method for the pebble layer, the rotary drilling of the pile casings is utilized, so that the hole wall of the drilling hole is kept stable in a sandy pebble layer and a region with complicated geological conditions, and the hole forming rate is improved.