The invention discloses a first assembly mechanism of a limiting switch assembling machine. The first assembly mechanism of the limiting switch assembling machine comprises a top head loading device, a spring loading device and a feeding device mounted on a position change bracket; the spring loading device is arranged on the front side of the top head loading device; the feeding device is arranged on the right side of the spring loading device; and the top head loading device includes a top head vibration disc, a linear feeder, a vibrator, a gantry bracket, a glue injecting head, a bin bracket, a glue injecting bin, a guide chute, a guide push block and a top head push-pull cylinder. Through the mode, the first assembly mechanism of the limiting switch assembling machine can replace workers to automatically assemble and change positions of workpieces, so that the labor force is saved, and the production cost is reduced.