High quality picosecond laser pulse can be generated from gain-switching laser diode system, which is composed of gain-switching laser diode, injection locking technology, pulse compressing and reshaping technology, as well as pulse amplification technology. The recent research progress of gain-switching laser diode system prove that pulse with higher output power, narrower pulse width, higher pulse quality and more flexible tunability can be achieved with the system. As a result, ultrafast gain-switching laser diode system has been used in much more new fields. The research progress in the above technical aspects are reviewed, and the new applications of ultrafast gain-switching laser diode system are introduced briefly. This may offer a reference for the future research in this field.