Supporting device and underpinning method for beam supporting and column replacing

The invention relates to the field of building construction, and discloses a supporting device and an underpinning method.The supporting device comprises a plurality of supporting assemblies arranged side by side, and each supporting assembly is used for supporting a single structural beam; every two adjacent supporting assemblies are connected through a first connecting piece. The supporting assembly comprises at least two supporting pieces arranged in sequence, and every two adjacent supporting pieces are connected through a second connecting piece. The supporting piece comprises a supporting column and a jack arranged at the top of the supporting column, and the second connecting piece is connected with the supporting column; the supporting device is composed of the multiple supporting pieces, the first connecting pieces and the second connecting pieces in a matched mode, so that the supporting device has good stability; moreover, the supporting piece is composed of the supporting column and the jack, the