Abstract: During the process of single-electrode narrow gap submerged arc welding, the movement track of the electrode and nozzle in the groove and at the interchange of weld beads was analysed. According to this analysis the corresponding control parameters of the movement track were put forward. Through the design of software and hardware, the movement track was recalled and traced by using a single-chip computer. And, furthermor the movement track reappeared at the welding of top weld beads. The problem of continuous tracing of the top weld beads was solved and sound narrow gap welds could be obtained.