Abstract: In order to investigate the law of influence and mechanism of oscillating laser wire-feed welding for titanium alloys on weld formation, surfacing experiments on the surface of TC4 plates were conducted, and the welding process was observed using a high-speed camera. The results demonstrate that, compared with conventional laser welding, oscillating laser welding demonstrates a significant improvement in weld formation within an expanded process window. Wire feeding speed, oscillation amplitude, and oscillation frequency significantly affect the cross-section characteristic dimensions of the weld. According to the images captured by high-speed cameras, under conventional laser conditions, molten droplets predominantly exhibit a large droplet transition. When the oscillation amplitude of laser is set to 1 mm, stable liquid bridge transition is achieved at both 80 Hz and 160 Hz oscillation frequencies. However, when the oscillation amplitude is 2 mm, the droplet transition shifts to a solid-liquid mixing particle transition. Analysis reveals that the continuous action of the conventional laser on the wire increases the tendency of large droplet transition, resulting in violent molten pool fluctuations and irregular weld formation. In contrast, oscillating laser actively stirs the molten pool, promoting contact between the molten pool and the wire to form a liquid bridge and achieve uniform weld formation. However, when the oscillation amplitude is great, the laser fails to quickly melt the wire, causing the wire fracturing in the middle that generates solid-liquid mixing particles. These particles exhibit incomplete melting and spreading in the molten pool, ultimately leading to serrated weld edges.