In order to study the behavior evolution of nonmetallic inclusions in heavy rail steel, further control the inclusions of steel and improve product quality. The evolution of chemical composition, quantity, size, etc. of nonmetallic inclusions was investigated from an example U75V heavy rail steel based on sampling during the production process of the LFVDCC route, combined with oxygen and nitrogen analysis, molten steel composition analysis, nonmetallic inclusion analysis and thermodynamic calculation. The results show that the oxygen and nitrogen content in the production of U75V heavy rail steel process continues to decrease, and the final TO and ［N］ mass fraction are about 0.001 0% and 0.004 0% respectively. MnOSiO2Al2O3 type of inclusions are the main inclusions at LF start, which originated from deoxidation product. After the slagging, the MnOSiO2Al2O3 inclusions are converted into CaOSiO2Al2O3 type, and the Ca and Als brought by the alloying materials such as BaCaSi and FeSi are the main reasons for the result. When leaving the LF station，the inclusions are CaOSiO2Al2O3MgO with CaO and MgO content increased. CaOAl2O3MgO inclusions disappeared during VD refining, and CaOSiO2Al2O3 was mainly found in samples from VD vacuum broken to bloom. The proportion of inclusions of magnesiumaluminum spinel in the rail increases, and which is CaOSiO2Al2O3MgO type of inclusions. The thermodynamic calculation results show that the spinel inclusions in the rail are formed during cooling process, and the calculated value is consistent with the actual value.