Abstract: Powder metallurgy technology was proposed to prepare the pure iron soft magnetic material. The green of iron powders in different size distribution was compacted at different temperatures and pressures, and then was sintered in protective atmosphere. The results show that the appropriate size proportion of iron powders is helpful to increase compaction density. The suitable pressing temperature can effectively promote the powder flowability, avoid the formation of large-sized pores, and finally optimize the microstructures of iron powder green. The highest compaction density of atomized iron powders can achieve 7.35 g·cm^-3 in the warm compaction condition of at 140℃ and 800 MPa. Compared with the normal temperature compaction, the pore distribution of sintered body prepared by warm compaction is uniform. The density of sintered body increases with the increase of temperature. After sintered at 1250℃, the highest density of atomized iron powder compaction can reach 7.47 g·cm^-3. The magnetic properties of soft magnetic material are proportional to the density. The density compacted by iron powders in different size distribution is close to the theoretical. But in the mixed iron powders, the fine iron powders are mixed in the coarse powders, which hinder the movement of the magnetic domain wall, resulting in the phenomenon that the saturation permeability (M_s) is smaller (205.51 emu·g^-1) and the coercivity (H_c) is higher (7.9780 Oe).