The utility model provides an open joint type top arc-shaped curtain wall drainage device. The device comprises a water guide assembly and a water collection cavity, the water guide assembly comprisesat least two arc-shaped curtain wall plates. The water collecting cavity is positioned on the inner side of the curtain wall plate; the water collecting cavity extends in the arc direction of the curtain wall plate. The curtain wall plates are at least partially overlapped, a gap is formed in the end-to-end connection position of the two curtain wall plates, the outward side of the gap is upward,a water storage cavity is formed between the curtain wall plates and the water collection cavity, the gap is communicated with the cavity, and the cavity is communicated with the water collection cavity. The utility model provides a curtain wall with an arc-shaped top. The curtain wall comprises an arc-shaped curtain wall keel and further comprises the open joint type top arc-shaped curtain walldrainage device, the curtain wall plate is located on the outer side of the arc-shaped curtain wall keel and fixedly connected with the arc-shaped curtain wall keel, and the water collecting cavity islocated on the inner side of the arc-shaped curtain wall keel and fixedly connected with the arc-shaped curtain wall keel.