The present invention discloses a method for adopting the limonite and the siderite to produce iron powder and a reduction roaster. The material adopts the limonite and the siderite or the specularite, the hematite, and the sulphuric acid slag, the inclined rotary reduction roaster is used, the pressure of the furnace chamber is 250 to 350 Pa, under the deoxidizing atmosphere, the inert solid is rotated and moved to 650 to 900 DEG C from the low temperature, and is cooled and magnetized, and lastly become the iron powder through the dressing by magnetic separation. The present invention is adopted to produce the iron powder, the resources is rich and the production cost is low, and through the utilization of the powder metallurgy art, the iron content of the iron powder is controlled and the activation energy of the iron powder is reduced, and the chemical reaction ability is increased, thereby the output of iron powder is high, the quality is good, the iron powder is loose and porous, the specific surface is big, the apparent density is large, the manufacture cost of pellets sinter and steel smelting can be reduced greatly, and the iron powder can use directly to produce iron oxide red as well as H and N synthetic iron catalyst, or produce ultrapure iron powder.