The English wheel is a traditional forming machine, which is adept at forming sheet metal parts with compound curvatures. However, due to the lack of in-depth research into the laws of the forming process with an English wheel and the high reliance on skilled craftsmen, this forming technique is not widely used in the manufacturing industry. In this work, experiments were conducted to explore the effects of different process parameters and possible forming trajectories on the forming outputs. The forming processes were realized by a robot-assisted English wheel forming system. It is found that the curvature shaped on the sheet metal increases as the number of the forming passes rises, or the curvature of the bottom anvil grows. Meanwhile, the curvature is also strongly correlated with the inclination of the forming path with respect to the horizontal plane. The experimental results also show that the curvature of the sheet metal becomes larger when smaller path spacing is employed, while the variation pattern of this curvature value differs from each other when using different types of forming trajectories. Moreover, axisymmetric forming trajectories show relatively better feasibility in addressing forming tasks for sheet metal parts with mechanical structural symmetry requirement.