The utility model provides a building girder steel, the girder steel is formed by U type structure and box structural grouping, the girder steel receives the great position of hogging moment to adopt the box structure, and all the other positions adopt U type structure. Furthermore, the utility model also provides a connection structure of building girder steel includes steel sheet shear force wall, building carrier plate and foretell girder steel, the girder steel both ends respectively with steel sheet shear force wall fixed connection, the building carrier plate is transversely laid at two longitudinal arrangement and adjacent between the girder steel. Adopt the utility model discloses, because the girder steel adopts U type structure and box structural grouping to form, receiving the great department of hogging moment to adopt the box structure, all the other positions adopt U type structure to having reduced the roof beam cross -sectional height, having reduced the dead weight of steel quantity and girder steel, the bending resistance of girder steel and the ability of shearing can be guaranteed to the box structure simultaneously, have reached the target that increases the building layer number, have promoted the utilization ratio of space.