Abstract: SLM is one of the key technologies for rapid manufacturing of high-performance high-entropy alloy components. However, in the SLM process, the multi-parameter manufacturing space directly affects the microstructure of the material, thereby influencing the performance of high-entropy alloys. This study explores the comprehensive relationship among the multi-parameter manufacturing space, density, microstructure, and microhardness of SLM-manufactured Al_0.5CoCrFeNi bulk high-entropy alloy, providing theoretical references and a technical support for the SLM preparation of multi-parameter combination high-entropy alloys. The research results indicated that the optimal forming quality of the specimens was achieved with SLM process parameters of P = 100 W, v = 1500 mm/s, α = 67° and VED = 44.4 J/mm³, resulting in the lowest internal porosity, at 1.8%. Both lower and higher VED negatively impacted macroscopic forming quality. VED had a notable influence on phase distribution, grain morphology and average grain size. The SLM-manufactured Al_0.5CoCrFeNi bulk high-entropy alloy consisted of FCC and BCC phases, with the FCC phase content increasing from 99.73% to 99.98% as VED increased. The columnar grains became predominant, with the average grain size initially increases and then decreases. Low-angle grain boundaries exhibited an initial increase followed by a decrease, while high-angle grain boundaries showed the opposite trend. The microhardness first decreased and then increased to 244.3 HV, This trend is consistent with the pattern of mean grain size variation with VED in accordance with the Hall-Petch relationship.