Abstract: Study on preparation of phosphorous slag superfine powder with jet mill was made.The results showed that the specific surface area of phosphorous slag powder got smaller with the increase of flow velocity of raw materials，but did bigger with jet air pressure or crash air pressure.Under the prior conditions，i.e.flow velocity was 5 g/s，feeding air pressure was 0.75 MPa，and crash air pressure was 0.70 MPa，the specific surface area of phosphorous slag powder was 859 m²/kg and characteristic particle size was 5.91 μm.

Key words: jet mill, phosphorous slag, superfine powder