The invention relates to the technical field of foundation pit construction, in particular to an excavation construction method for a super-wide low-permeability silty deep foundation pit. The construction method comprises the following steps that the foundation pit is excavated in a low-permeability silty soil layer where foundation pit dewatering is not carried out, the action of earth berm under the super-wide characteristic of the foundation pit is fully used, excavation is conducted in a partitioned and layered mode, the earth berm is reserved by slotting a slot in the middle of the foundation pit, steel supports are erected, and the earth berm is excavated out, so that balance and stability of the earth berm and supporting structures in the foundation pit are ensured; and meanwhile, abnormal conditions of the foundation pit is closely concerned through foundation pit monitoring measurement, and the purposes of reducing interference of the supports to earth excavation equipment and accelerating construction progress are achieved. The stepped continuous excavation supporting construction is adopted, and excavation is conducted in a partitioned and segmented mode, so that layered, segmented, ordered and normalized foundation pit excavation is achieved, machine input is reduced, the number of times of earth relaying transferring is reduced, the machine using efficiency is improved, and repeated dispatching of machines in the excavation process is reduced.