In SAW panel welding, which involves single-pass welding on the front and back sides of a steel plate, careful selection of welding parameters is crucial to achieve optimal bead penetration and a smooth surface, preventing structural issues. However, for welding thick steel plates, a higher current may cause excessive weld deposition leading to bead protrusion. Current methods for reducing bead height, such as decreasing welding speed or machining a Y-shaped groove, can result in reduced productivity. This study investigated the effect of various welding parameters on bead height during bead-on-plate welding with tandem SAW. Welding current, voltage, and deposition amount were measured, and the surface shape of the bead was recorded using a laser displacement sensor to ensure continuous data after welding. Results showed that the bead height increased proportionally to the deposited amount in single-pole SAW. However, in tandem SAW, the interaction between the leading and trailing electrodes caused variation in bead height, even with the same deposited amount. Molten pool flow analysis revealed that bead height decreased as flow speed in the width direction of the bead at the trailing electrode position increased. However, excessive flow speed led to instability of the molten metal between the electrodes, resulting in uneven weld beads. During the welding process, this instability caused a short disappearance of the leading arc and fluctuations in the trailing voltage, increasing the height of the bead.