Abstract: A kind of white phase distributing along grain boundary were found in the microstructure of 82MnA steel billet when regular metallographic examination. Instruments such as direct-reading spectrometer, optical microscope, micro-hardness tester, scanning electron microscope and X-ray energy spectrometer were used to analyze the white phase. The results show that the white phase in 82MnA steel billet was phosphide Fe3P with high phosphorus content and high hardness. Most of the phosphide Fe3P distributed along the grain boundary and had obvious boundary and liquid optional solidification characteristic, and it was harmful to the steel.