Foundation pit enclosure structure capable of realizing supporting while excavating and foundation pit excavating method

The invention relates to a foundation pit enclosure structure capable of realizing supporting while excavating and a foundation pit excavating method. The geological condition is shown in a targeted way according to the excavation, corresponding supporting parameters are adopted, the supporting reliability is improved, the measures of the enclosure structure are more reasonable, and the construction cost is effectively reduced. The foundation pit enclosure structure comprises an advance support (10), a primary support (20) and a supporting system, wherein the advance support (10) is exerted on a pre-reinforcement rock soil body formed in the rock soil at the outer side of a foundation pit excavation line, the primary support (20) is fully and annularly exerted on the vertical excavation surface of a foundation pit, a sealed rock surface body is formed, the supporting system comprises vertical steel enclosing purlins (30), steel transverse supporters (41) and steel inclined supporters (42), the vertical steel