The invention discloses a selective laser melting rapid forming device for directly manufacturing large-size compact parts, which mainly comprises a laser array, an optical system array, a forming cylinder, a forming cylinder vertical sectional heating thermal-insulation structure, a forming cylinder weight balancing system, a substrate leveling device, a double-recovering cylinder, a double powder storing box, a double quantitative powder sending and discharging device, a powder paving device, a protective atmosphere cover, a gas purifying system and a control system, wherein an adopted optical system is composed of a plurality of optical system units and a mechanical moving platform, and the coverage area of the optical system can be randomly expanded or reduced. The size of the parts manufactured by using the selective laser melting rapid forming device provided by the invention is more than the size of the parts manufactured by using the existing national and foreign selective laser melting processes. The forming efficiency is multiplied while the forming precision, the parts complexity and the mechanical property are not changed.