Middle floor slab based on inner supporting system and construction method of middle floor slab

The invention discloses a middle floor slab based on an inner supporting system and a construction method thereof, and the construction method comprises the following steps: S1, designing a construction drawing, and constructing three sectional supporting structures which are divided into a first concrete support, a second steel support and a third steel support; s2, each middle plate support in the foundation pit and inner supporting structures around the middle plate support are divided into a plurality of groups, and one group of inner supporting structures comprises a group of stand columns and middle longitudinal beams and comprises a plurality of groups of middle plate supports; s3, hoisting a bottom plate; s4, dismantling the third steel support in the range of the first group; s5, a first set of stand columns and middle longitudinal beams are constructed; s6, middle plate supports in the first group are constructed; and S7, circulating construction is conducted on the remaining groups in sequence. Mid