Plasma arc welding (PAW) has several advantages over traditional gas tungsten arc welding (GTAW) process. However, due to its sensitivity to welding parameters, this process has not been widely used in industry, especially for manual welding applications where variations in welding parameters are substantial. This paper introduces and implements a model predictive control (MPC) method to adjust welding current in order to compensate the effects from these variations during manual plasma welding operation. A linear model with adequate accuracy has been selected for the design of control system. Closed-loop control experiments verified the effectiveness of developed control system.