The mechanical properties and alloying behavior of Fe-base compacts were investigated. Fe-P and Cu-P master alloys were used for preparing Fe-3Cu-3Ni-P compacts varying the composition of phosphorus from 0.2 wt% to 0.6 wt%. The compacts were sintered at 1120℃ for various time up to 180 minutes under dried hydrogen atmosphere. Remarkable increase in hardness of sintered compacts was observed by adding the phosphorus, however the tendency and the amount of increase in hardness were different with the type of phosphorus compound used. The compacts which prepared from powder mixture containing Cu-P compound powder showed higher values of sintered hardness than the specimens containing Fe-P compound powder. The dimensional expansion took place at early stage of sintering ; during heating the specimen to sintering temperature. Most of the dimensional expansion was attributed differently by the type of used P-compound ; the penetration of liquid phase between Fe particles for the compacts containint Fe-P compound powder, and the alloying phenomena for the compacts containing Cu-P compound powder during heating and sintering. The added P compound powder formed eutectic alloy during heating and melted at lower temperature than the melting point of P-compound. The liquid phase smeared out to Fe matrix and formed solid solution leaving pore at the site of liquid phase located.