By the aid of the spectrum detecting device of welding arc, the droplet transfer spectral information of pulsed MIG welding has been researched experimentally. Results show that the arc spectral information can reflect well droplet transfer process in pulsed MIG welding. Many kinds of spectral information modes of droplet transfer have been found, which can reflect various droplet transfer types, such as one-peak-zero-base, one-peak-one-base, one-peak-two-base, two-peak-zero-base, two-peak-one-base, two-peak-two-base, three-peak-zero-base and so on. Especially, they can sharply and clearly reflect multiple drops spray transfer in the period of pulse peak. These spectral information have excellent character and therefore the spectral real-time and precise control of droplet transfer in pulsed MIG welding will be realized.