Abstract: The plume can be divided into two parts: the fluctuating portion that emerges from the keyhole, called the lower fluctuating plume, and the portion that resembles a focused laser beam, referred to as the narrow plume. The changes in the morphology of these two plume parts and their influence on the welding process were studied. The results show that with increasing welding speed, the eruption direction of the lower fluctuating plume gradually deviates from the laser beam in the opposite direction of welding. The height of the narrow and long plume gradually decreases until it disappears. The effect of plume glow on the depth/width of the melt gradually decreases until it disappears. The forming quality of the weld surface gradually deteriorates. Increasing the welding speed reduces the negative impact of the narrow and elongated plume on the depth/width of the melt. The impact of the lower fluctuating plume on the back wall of the keyhole causes the length of the orifice along the welding direction to become larger, increasing spatter and reducing the forming quality of the weld surface.