After purifying and milling the revolving furnace sludge were nitrided at NH_3/H_2 atmosphere.The phase structure for nitrogen specimens were checked by Mssbauer spectroscopy and X-ray diffraction,etc.The results show that at following conditions : milling for 2h in Ar gas,reducing at temperature of 550℃ for 2h,nitriding at 550℃ for 3h in NH_3/H_2 atmosphere,the γ′-Fe_4N magnetic powder can be synthesize,the content ≥91%.