The invention relates to an automatic escalator step chain structure capable of preventing shaft pins from loosening, and belongs to the technical field of automatic escalator members. The automatic escalator step chain includes a step chain rail and a step chain; the step chain rail forms a drawing main wheel rolling channel; the step chain includes a plurality of chain joint units which are mutually connected in a cycle manner; each chain joint unit includes inner chain sheets which are arranged in pairs and parallel to each other, outer chain sheets which are arranged in pairs and parallel to each other, shaft pins for hinge-jointing the inner chain sheets and the outer chain sheets, and steel wheels and drawing main wheels which are corresponding to the inner sided of the inner chain sheets and arranged on the shaft pins in a front and back corresponding state; the drawing main wheels and the drawing main wheel rolling channel form a rolling pair; the automatic escalator step chain includes a shaft pin loosening detection mechanism; and the shaft pin loosening detection mechanism is fixed on the step chain rail and is corresponding to a front side surface and a back side surface of the step chain. The excellent automatic online detection efficiency and the excellent detection effect are embodied, the working load of detection workers are reduced, safe operation of steps can be ensured, and accidents can be avoided.