Building expansion joint

The utility model discloses a building expansion joint which comprises moving plates, the two moving plates are symmetrically arranged, a buffer strip is fixedly connected between the adjacent moving plates, a scale is arranged, a transverse strip is fixedly connected to the outer side of the scale, and the part of the transverse strip is fixedly connected with a second adapter block. Second screws are movably connected to the inner sides of the second adapter blocks through second limiting holes, moving plates are in threaded connection with the outer sides of the second screws, and after the moving plates and the buffer strips are installed through embedded parts, the moving plates on the two sides are stressed to move towards the center direction along with long-time use; the moving plate on one side drives the sleeve frame to translate through the top plate and the first switching block, the moving plate on the other side drives the ruler to move through the transverse strip and the second switching block