The invention discloses an opposite supporting structure in a foundation pit reflex angle position. The opposite supporting structure comprises internal surrounding purlin structural steel, external surrounding purlin structural steel, triangular connecting base and struts, wherein the internal surrounding purlin structural steel is connected with a cement continuous wall on the periphery of the foundation pit; the external surrounding purlin structural steel is connected with a flange on one side of the internal surrounding purlin structural steel, which is far away from the cement continuous wall; the triangular connecting base is connected with the internal surrounding purlin structural steel and the external surrounding purlin structural steel; the struts are connected with the triangular connecting base through strut connecting pieces. The triangular connecting base adopts an isosceles right triangle in a whole, a part of the beveled edge of the triangular connecting base is connected with the internal surrounding purlin structural steel on one side of the foundation pit reflex angle position through bolts, and the other part of the beveled edge of the triangular connecting base is connected with the internal surrounding purlin structural steel and the external surrounding purlin structural steel on the other side of the foundation pit reflex angle position through a first filler block, a second filler block and a third filler block.