The effective manipulation of two-dimensional (2D) magnetic order is crucial for both exploring novel physical phenomena and developing multifunctional magnetic electronic devices. Intrinsic interfacial coupling in van der Waals heterostructures provides a promising pathway for efficient, low-power magnetic manipulation without relying on external fields or charge currents. The strong spin-orbit coupling and topologically protected surface states of topological insulators make the heterostructures based on topological insulators ideal for modulating interface magnetism through mechanisms such as charge transfer or the proximity effect, establishing them as a premier platform for interfacial magnetic control. In this work, a van der Waals heterojunction composed of the ferromagnet Fe₃GaTe₂ and the topological insulator Bi₂Te₃ is constructed via mechanical exfoliation and deterministic transfer techniques, and the effect of Bi₂Te₃ interface interactions on the Fe₃GaTe₂ magnetism is explored. A comparison of microscopic magnetic domain evolution between pristine Fe₃GaTe₂ and Bi₂Te₃/Fe₃GaTe₂ heterojunction at different temperatures shows a significant enhancement of the magnetic ordering in Fe₃GaTe₂ by the topological interface. Magneto-optical Kerr effect (MOKE) measurements further confirm that the Curie temperature of the heterojunction increases by approximately 20 K and the Kerr signal exhibits an anomalous sign reversal. These results reveal the significant role of topological interface effects in modulating 2D magnetism, thereby laying experimental foundation for developing high-performance spintronic devices.