Abstract: A method for synchronous powder-feeding space laser cladding and three-dimensional forming includes: dividing a three-dimensional solid into a plurality of forming units according to a form simplification and nozzle cladding scanning accessibility principle, and dividing each forming unit into a plurality of layers; employing a single-beam gas-carried power-feeding mode in a hollow annular laser; controlling a mechanical arm (7) to drive an in-laser powder-feeding nozzle (1) to move and scan along a predetermined trajectory in a filling area and a boundary area of the layer; and sequentially conducting cladding and stacking formation of the layer for the entire unit. A device includes an inside-laser powder-feeding nozzle (1), a laser generator (6), a mechanical arm (7), a control module (4), a transmission optical fiber (5), a gas-carried powder feeder (3) and a gas source (2).