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Tungsten wire with high strength and toughness for silicon wafer cutting in photovoltaic industry is a new hot research content. In order to improve the strength and processing performance of tungsten wire, tungsten alloy containing 0.5 wt%La2O3 was prepared by powder metallurgy method. The hot deformation behavior and microstructure evolution of tungsten lanthanum alloy were studied. Studies have shown that the alloy is extruded to grow fine grains, and its texture structure mainly presents two directions. The grain size of the instability zone is too large, and there are obvious cracks. With the decrease of strain rate and the increase of temperature, the recrystallization ratio of the alloy increases gradually, showing a partial equiaxed grain structure. The recrystallization ratio reaches the maximum at 1600 °C/0.01s−1, but it is still not completely recrystallized. Lanthanum oxide gradually aggregates to the grain boundary during the hot deformation process, which improves the thermal deformation activation energy of tungsten. The Q value is about 410.018 kJ/mol, which improves the high temperature strength of tungsten alloy. The compressive strength of tungsten alloy at high temperature is about 10% higher than that of pure tungsten. Combined with the hot processing map, the optimum process parameters of tungsten alloy were determined to be 1400 °C–1600 °C, 0.01–0.05s−1. The φ35.5 μm ultra-fine tungsten wire was prepared according to this parameter. The microstructure of tungsten wire is uniform and dense, and there are no cracks and defects. The tensile strength of tungsten wire is extremely high, reaching 5723 MPa.