Single-phase equiatomic AlCrTiV high-entropy alloy has high hardness and relative low density. Further hardness increase was achieved through the addition of lightweight microalloying elements, based on calculation of phase diagram (CALPHAD) modeling. According to the results of CALPHAD calculation, microalloying equiatomic AlCrTiV high-entropy alloy with boron, carbon, and silicon will result in the formation of secondary phases. CALPHAD calculation also shows addition of lightweight elements can affect the order-disorder transition of microalloyed AlCrTiV high-entropy alloy. Dual-phase microstructure consisting of BCC_B2 matrix and an intermetallic phase is observed in these microalloyed alloys. Electron microscopy characterization confirms that the experimental results are consistent with CALPHAD prediction. Microalloyed AlCrTiV alloys have density close to 4.5gcm(-3) and hardness up to 710HV. Compared to other high-entropy alloys, the microalloyed AlCrTiV alloys have a good combination of specific hardness, low cost, and ease of manufacturing, and thus they are promising for lightweight applications.