Aluminum alloy liquid cold plates are important parts of heat dissipation for the electronic equipments used in aerospace and national defense industries. Usually they have complex outlines and microchannels; thus, they are suitable to be fabricated via selective laser melting (SLM) additive manufacturing technology. To elevate the build rate of the SLM-processed liquid cold plates, a high-power (1 kW) SLM apparatus was used to process AlSi10Mg alloy in this study, and the densification behavior, microstructure, mechanical properties, and minimum hole diameter of the SLM-processed samples were investigated. Results show that the relative density of the high-power SLM-processed samples first increase with the increase in laser volume energy density, and then remain unchanged at high laser volume energy densities. To obtain a high relative density of more than 99.5%, the laser volume energy density should be set in the range of 47.6‒200 J/mm³ during the high-power SLM process. The microstructure of the as-fabricated sample comprises α-Al cellular dendritic matrix possessing a 〈100〉 texture along the building direction and reticular eutectic Si. Owing to the comprehensive effects of grain boundary, solid solution, and second phase strengthening, the tensile strength, yield strength, and elongation of the high-power SLM-processed samples were (433±10) MPa, (267±8) MPa, and (5.5±0.5)%, respectively, which were higher than the corresponding values of the die casting AlSi10Mg. When the 1 kW high-power laser was used in the SLM process of AlSi10Mg, the minimum horizontal and vertical hole diameters that could be fabricated were 0.6 mm and 0.4 mm, respectively, which could satisfy almost all design and forming requirements for a liquid cold plate. Based on the above technology, local simulation parts of an aluminum alloy liquid cold plate were successfully fabricated using high-power SLM, and the build rate was up to 75.6 cm³/h.