Dual-phase steel is a mixture of ferrite matrix and martensitic islands distributed at grain boundaries with the possible addition of bainite. Its formability, capacity to absorb crash energy, and ability to resist fatigue make it a desirable material for use in the automotive industry to enhance automobile’s strength and reduce its weight. However, the resistance spot weldability of dual-phase steel is sometimes limited by a propensity for weld metal failure due to the welding process. To improve its weldability, a servo gun spot welding system is introduced to control electrode force during the welding process. The paper take 1.5mm DP600 steels as an example, experimental data shows that by optimizing electrode force during welding process, the width of weld lobe can be enlarged from 0.9kA to 2.1kA and the weldability of dual phase steel is improved greatly.