High-silicon aluminum alloys, due to their excellent thermal conductivity and high specific strength, are crucial in aerospace thermal protection structures. However, the silicon particles within these alloys complicate machining processes. Longitudinal-torsional ultrasonic vibration-assisted minimum quantity lubrication (LTUVAM & MQL) cutting has proven effective in enhancing the machinability of homogeneous materials, but its application in high-silicon aluminum alloys requires further study. In this research, single-factor experiments were conducted to investigate how different cutting parameters affect cutting force, temperature, and workpiece surface quality during LTUVAM & MQL milling of Al–50% Si (mass fraction) alloys. Comparisons were also made between the machining performances of LTUVAM & MQL, minimum quantity lubrication (MQL) milling, longitudinal-torsional ultrasonic vibration-assisted milling (LTUVAM), and conventional milling (CM) for Al–50% Si alloys. The results indicated that LTUVAM & MQL offered the best cutting performance, followed by LTUVAM and MQL, with CM being the least effective. This study provides valuable insights and important references for improving the machining efficiency and quality of high-silicon aluminum alloys.