Abstract: A laser powder bed fusion forming device for a large-size ring/frame-shaped metal piece. Said device includes a forming cylinder, a substrate, a galvanometer array and a dust removal module. The forming cylinder is ring/frame-shaped and is adapted to the inner and outer contours of the ring/frame-shaped metal piece to be formed. The substrate is also ring/frame-shaped and is arranged inside the forming cylinder. The galvanometer array is located above the forming cylinder, includes a plurality of galvanometer systems, and the corresponding scanning areas thereof cover the upper surface of the forming cylinder. The dust removal module is located between the forming cylinder and the galvanometer array, and is used for forming a circulating air flow field which is distributed along the radial direction of the ring-shaped metal piece or along the circumscribed circle of the horizontal cross-section of the frame-shaped metal piece or along some other specific directions.