Prevent unconstrained expansion joint of unstability

The utility model provides a prevent unconstrained expansion joint of unstability, including left side takeover, right takeover, bellows and protection casing, the bellows includes first bellows, second bellows and third bellows, the left end of second bellows links to each other through a guider with the right -hand member of first bellows, and the right -hand member of second bellows links to each other through the 2nd guider with the left end of third bellows, and the left end of first bellows is taken over with a left side and is linked to each other, and the right -hand member of third bellows is taken over with the right side and is linked to each other, the utility model discloses a prevent unconstrained expansion joint of unstability can prevent phenomenons such as expansion jointtwist and warping and unstability, guider has the direction function, when the expansion joint stretches out and draws back, plays the cushioning effect, the protection casing provides the protectionfor the expansion joint, a