The upper soft soil layer is mainly cohesive soil in coastal quaternary overburden layer, which has great effects on the hole and the final pile quality in the drilling process of submersible drill. The quality problems are water emitting from the top of pile, mud mixed in pile body, diameter shrinkage, reinforced steel exposing, bit balling and hole verticality deviation, and these related causes are analyzed. The paper summarizes the key points of boring control technology by submersible drill in clay, including the control in construction preparation stage, construction stage and hole cleaning stage, as well as other measures.