Due to the pointbypoint, linebyline and areabyarea localized forming characteristics of laser additive manufacturing (LAM) process, it is required to carry out the microscopic—mesoscopic—macroscopic crossscale structure and performance control of LAM of metal components, in order to realize the effective control of balling effect, porosity, deformation, cracks and other typical metallurgical defects. In this paper, the selective laser melting (SLM) precision manufacturing of hardtoprocess aluminum alloy is performed. In the mesoscopic scale, the thermodynamic behavior of the laser melting/solidification of the metal powder is disclosed and the formation and inhibition mechanisms of balling effect are revealed. In the microscopic scale, the mechanism of the surface tension of the melt in the molten pool on the bubble motion and melt densification is clarified. In the macroscopic scale, the thermal mechanism and the stress formation and deformation behavior of LAM processed components are proposed. This study can provide the physical basis and key process control method for the structure and performance control of highperformance and complex metal components by LAM.