The invention discloses an inner obliquely beam supporting structure for an oversized-area deep foundation pit. The inner oblique beam supporting structure comprises a pouring
pile and an inner oblique beam, wherein the pouring
pile is arranged at the edge of the foundation pit, the upper end of the inner oblique beam is fixedly connected with a top beam or a
waist beam arranged on the pouring
pile, and the lower end of the inner oblique beam is fixedly connected with a
basement base board. The invention further discloses a construction method for the supporting structure. The construction method comprises the following steps of constructing a
fender post, constructing the pouring pile in the
fender post, excavating earth in a graded mode to the elevation of a
cushion layer of the top beam, constructing the
reinforced concrete top beam and maintaining the
reinforced concrete top beam to the design strength, excavating earth in a graded mode to the design elevation of the pit bottom except earth outside a reversed stereobate, constructing
basement base boards except
basement base boards outside the reversed stereobate, constructing a
branch oblique beam supporting seat, constructing the inner oblique beam, and excavating and removing the reversed stereobate. A deep foundation pit inner support constructed according to the supporting structure and the construction method is reliable in technique, convenient to operate, obvious in benefit and capable of meeting requirements for
energy conservation and environment protection.