Polar coordinate positioning form big arm machining tool and method

The invention relates to a polar coordinate positioning form big arm machining tool and method. The machining tool comprises tool assemblies, a first connecting piece and a second connecting piece. One end of a big arm is connected with the tool assemblies through the first connecting piece, and the other end of the big arm is connected with the tool assemblies through the second connecting piece. The tool assemblies are fixed to a movable working platform of a machine tool. The polar coordinate positioning form big arm machining method comprises the steps that the two tool assemblies are arranged in the opposite directions and located on the same straight line, the big arm is hoisted between the two tool assemblies and connected through the first connecting piece and the second connecting piece, a center adjusting mechanism is adjusted for center adjusting, the center adjusting mechanism is fixed after center adjusting is finished, and machining starts to be conducted on the big arm. According to the polar c