The invention discloses a flexible connecting and mounting structure for a double-helix circular structure spiral staircase. The flexible connecting and mounting structure comprises a building structure (1), a staircase structure, telescopic energy-accumulating equipment (2) with buffering performance, and a steel channel bracket (4), wherein the staircase structure is connected to the building structure (1) through the energy-accumulating equipment (2), the steel channel bracket (4) and the energy-accumulating equipment (2) in sequence; a rubber buffering belt (6) is arranged between the building structure (1) and the staircase structure; the energy-accumulating equipment (2) comprises iron plates (3), a bolt (5) and a spring; the spring (5) passes through the iron plate (3); the spring is arranged on the bolt (5); the iron plate (3) at one side of the energy-accumulating equipment is connected with the steel channel bracket (4); the iron plate (3) at the other side of the energy-accumulating equipment is connected with the building structure (1) or the staircase structure. By adopting the flexible connecting and mounting structure, the structural damage in rigid connection of the spiral staircase can be reduced effectively, and the stability, adaptability, comfort and attractiveness of the staircase are improved; construction is easy and feasible.