The utility model discloses a building foundation structure outside silt matter weak soil cutting means, crossbeam including making the handle simultaneously is in with the setting a pair of bracing piece that be used for insert weak soil of crossbeam on with one side, the first end of a pair of bracing piece with the crossbeam is fixed, and the second end is connected with the both ends of cutting rod respectively, the second end of bracing piece sets up to doing benefit to the guide structure who inserts the weak soil. Compare and get soil backfilling in the tradition, the utility model hasthe advantages of it is following: (1 )The action of fetching earth is decomposed, and efficiency improves. (2 )The action range is little, requires not highly to the operating space. (3 )Improve thework efficiency.