Foundation pit supporting system and construction method thereof

The invention relates to the field of foundation pit supporting, in particular to a foundation pit supporting system and a construction method thereof. According to the key points of the technical scheme, the structure comprises a plurality of sheet piles which are fixed to a foundation pit and arranged on the pit walls of the two opposite sides of the foundation pit correspondingly, and the sheet piles are provided with fasteners; the reinforcing keels are movably buckled in the fasteners in the horizontal direction and used for enabling the multiple sheet piles to be in mutual stress association; the support assembly is located between the sheet piles on the two sides of the foundation pit, and a power assembly is arranged on the support assembly; the telescopic supporting assembly is detachably arranged on the support assembly, the two ends of the telescopic supporting assembly are each provided with a telescopic movable supporting part, the power assembly is connected with the telescopic supporting assemb