The invention discloses a motion control method suitable for automatic welding of a complex curve device. The motion control method comprises the following steps: a three-dimensional motion control card is plugged in a PCI bus interface of an upper computer, and is connected with an automatic welding bench through a motor; the three dimensional spatial structure of a to-be-welded device is simulated on the upper computer; a control instruction is sent to the three-dimensional motion control card according to the three dimensional spatial structure of the to-be-welded device; the three dimensional control card controls the working state of the motor according to the control instruction; the motor controls the welding bench to conduct linkage according to the predetermined motion of the three dimensional spatial structure of the to-be-welded device; the welding bench conducts automatic welding on the to-be-welded device, and feeds back current welding coordinate to the upper computer in a real-time manner. The motion control method is suitable for welding of a complex curve path, and has the advantages that the motion control method is low in cost, flexible to control, and high in work efficiency and automation degree.