High-entropy alloys (HEAs), also called multi-principal-element solid solution alloys, generally exhibit high-temperature structural stabilities and excellent properties. Similar to the traditional solid solutions, the stabilities and properties of HEAs were also determined largely by chemical short-range interactions between elements. In recent years, we have developed a structural model, i.e., the cluster-plus-glue-atom model, for the description of chemical short-range orders in solid solution alloys. Thereof, the composition and structure characteristics of HEAs in Al-TM (TM: transition metals) systems were investigated using this new structural tool, where Al is regarded as the main solute that interacts with the TM multiple elements as a whole. The relevant cluster-based local structural units and composition formulas were then extracted, and a HEA alloy of [Al-M14]Al1 (M= Co1/5Cr1/5Fe2/5Ni1/5) was designed to possess prominent tensile properties, which is attributed to a superalloy-like microstructure of cuboidal B2 nanoprecipitates coherently embedded in the BCC matrix.