Building outer wall surface system

The utility model discloses a building outer wall surface system which comprises a cross beam and a wall panel, the wall panel is fixedly connected with the cross beam through an adapter assembly, the adapter assembly comprises a first adapter piece and a second adapter piece which are arranged at the two ends, opposite to the cross beam, of the wall panel, the first adapter piece is fixed to the cross beam through a bolt, and the second adapter piece is fixed to the cross beam through a bolt. An inserting groove part is arranged on the first adapter, an inserting part inserted into the inserting groove part is arranged on the second adapter, a first connecting part is arranged at one end, opposite to the wall panels, of the first adapter, a second connecting part is arranged at one end, opposite to the wall panels, of the second adapter, and a gap between every two adjacent wall panels is filled with weather-proof sealant. Compared with the prior art, not only is the structure simple, but also the firmness i