Fabricating high-performance large-size thermoelectric (TE) films with insulating substrates remains a major bottleneck for high-efficiency TE cooling in-plane heat dissipation. Herein, we have developed a multi-beam spark plasma sintering (MB-SPS) technology and used it to successfully prepare a series of high-performance large-size Bi_0.5Sb_1.5Te₃/epoxy (BST/EP) TE films with insulating substrates (MB-BST/EP films). We found that the {000l} preferential orientation factor of BST in the MB-BST/EP films is about 69%, increased by 72.5% as compared with that of conventional SPS BST/EP films (C-BST/EP films), thus achieving remarkable enhancement in their electrical transport properties. The maximum power factor of the MB-BST/EP films is about 2.47 mW m⁻¹ K⁻² at 300 K. The maximum dimensionless figure of merit (zT) of the MB-BST/EP film without a substrate and MB-BST/EP film with an insulating substrate are about 0.91@350 K and 1.38@340 K, respectively. The maximum cooling temperature difference of the single-leg device fabricated with the MB-BST/EP film is about 1.7 K, an increase of 2.4 times as compared with that of the device fabricated with the C-BST/EP film. In particular, the microstructures and electrical transport properties of the MB-BST/EP films are almost the same over a large-size area of 25 mm in diameter. Our work demonstrates that the MB-SPS provides an effective approach to prepare high-performance large-size TE cooling films with an insulating substrate.