The invention belongs to the technical field of iron and steel metallurgy and the field of gas-solid heat exchange or thermal reaction, and relates to a suspended reduction process of iron-containing materials and a secondary suspended reduction furnace device for implementing the process. In the injection reducing furnace, the gas phase and the solid phase flow upwards in parallel and the gas phase and the solid phase are in full contact, with large heat-transfer coefficient and large mass-transfer coefficient, so that the iron-containing materials are reduced and dried quickly and the retention time of material granules in the system is greatly shortened. The heat efficiency of the system is greatly increased. The thermal loss is reduced below 1800 kilocalories per kg of reduced iron-containing materials. The suspended reduction process has the advantages of high system stability, compact equipment installation, small size, low investment, high production capacity, high product metallization rate, controllable metallization rate within the range from 85% to 97%, and uniform product quality.