Building bridge expansion joint

The invention relates to the field of buildings, in particular to a building bridge expansion joint which comprises a plurality of main beams, a fixing plate and a bearing plate which are sequentially connected from bottom to top, a gap is formed between every two adjacent main beams, mounting grooves are formed in the upper ends of the main beams and communicate with the gaps, and the mounting grooves communicate with the bearing plate. A mounting groove is formed in the main beam, the fixing plate is fixedly connected to the groove bottom of the mounting groove, a lubricating groove is formed in the upper end of the fixing plate, the bearing plate is slidably connected to the upper end of the fixing plate, and an oil supplementing opening is formed in the groove wall of the lubricating groove. One end of the oil supplementing pipe is communicated with the oil supplementing tank, and the other end of the oil supplementing pipe is communicated with the oil supplementing opening. Oil in the oil supplementing t