The invention provides a closed type heavy-load thin wall light-duty pulley device and belongs to the technical field of heavy industrial machinery. The device comprises an end cover, a wheel hub, two webs and a rope groove which are annular and are connected in sequence from inside to outside, and further comprises a shaft which is arranged inside an inner ring of the end cover, a bearing for supporting the shaft and an inner ring supporting sleeve for positioning the bearing. The two webs are located at the positions on the two side faces of the pulley device and are at the same radial position of the pulley device. The wheel hub and the end cover are fixed by a stainless steel wire rope; an outer ring of the end cover is connected with the wheel hub; a gap being not more than 0.1mm is formed between the inner ring of the end cover and the inner ring supporting sleeve. An inner cavity composed of the wheel hub, the end cover, the inner ring supporting sleeve and the shaft is fully filled with lubricating grease to form a closed structure. The closed type heavy-load thin wall light-duty pulley device is free of maintenance; the lubricating grease can be fully filled in one time and does not need to be replaced within 4-5 years; meanwhile, the pulley device which has lighter self weight, greater load and smaller wall thickness is effectively realized and the service life of the pulley device is greatly prolonged.