The invention relates to a laser processing system which is capable of selectively sintering material powder for forming a firm component. The system consists of a laser light source, a light beam processing component, a reflecting component, a baffle plate, a forming structural component, a clamping structure, a structure component base, a powder spreading brush and a sealing cavity. In the system, by inverting the forming structural component and a processed laser beam, residual powder is effectively ensured not to be contained in the inner part of the sealing cavity when the sealing cavity is closed during selective laser sintering.