In this study, we used the dual-arc volumetric modulated arc therapy (dac-VMAT) technique to identify the most optimized multileaf collimator (MLC) angles that minimize the dose to the hippocampus and to analyze the underlying factors. Our findings provide a valuable reference for clinical treatment planning. Ten patients with brain metastases who had undergone whole-brain radiotherapy (WBRT) were included in this study. A dac-VMAT plan for HA-WBRT with different MLC angles was designed for these patients to minimize the dose to the hippocampus, while meeting the dosimetric limit for the PTV and other OARs. Parameters such as conformity index (CI), homogeneity index (HI), dose to 2% of the PTV (D_2%), dose to 98% of the PTV (D_98%), monitor units (MUs), treatment time (TT), and doses to OARs, including the hippocampus, lens, eyeballs, optic nerves, and chiasm, were analyzed to assess the advantages and disadvantages of different MLC angles. The results showed that minimal differences were observed in PTV parameters across various MLC angles, and the MUs for the 60°and 300° angles were lower than those for other angles. The hippocampus dose at 60°/300° was significantly lower than that at other MLC angles; other OARs showed no significant differences. At 60°and 300° MLC angles, the long axis of the hippocampus was perpendicular to the direction of movement of the MLC blades, allowing for comprehensive shielding of the hippocampus. The MLC configuration led to a better PTV conformity, reduced leakage and scattered beams, fewer MUs, and less complicated treatment plans. Thus, the dual-arc symmetrical MLC VMAT has an optimal HA-WBRT angle of approximately 60° and 300° MLC.