When the size of aluminum oxide inclusions in steels is too large and the edges and corners are sharp, they can be regarded as the main source of cracks during the process of steel wire drawing, and these cracks substantially affect the performance of the steel. The refinement or removal of inclusions in steel is important. Since the amount of alloying elements added to steel is relatively small compared to that in the molten steel and there are errors during the experiments and analyses, the reaction of inclusions is magnified and studied by varying the proportions of rare earth lanthanum oxide powder and alumina at a high temperature of 1 600 ℃. The amount of powder that is added affects the phase change and size of the inclusions. A high-temperature box furnace is set to increase the temperature, keep warm and cool, and X-ray diffraction and Raman spectrometry are used to analyze the specific changes of lanthanum aluminum oxide. The results show that with increasing amounts of La₂O₃, the LaAl₁₁O₁₈ phase is formed first, followed by the LaAl₁₁O₁₈ and LaAlO₃ phases. As the peak intensity decreases, the full width at half maximum increases and the grain size decreases. Then, the characteristic peak intensity of LaAl₁₁O₁₈ disappears, leaving only a decreased amount of the LaAlO₃ phase, and no new phase is formed. Combined with the mathematical model for the average grain size of HW, R² for samples 1^#, 2^#, 3^# and 4^# is calculated to be 0.990 25, 0.962 59, 0.987 1, and 0.989 76, and the grain sizes are 6.08, 2.88, 7.67, and 4.75 μm, respectively. Sample 2^# has the smallest grain size herein, and sample 3^# has the largest grain size herein, indicating that an appropriate ratio of lanthanum oxide and aluminum oxide can promote nucleation and reduce the grain size. Through Raman spectrometry, it is observed that with a decrease in the Al₂O₃ ratio, the Raman characteristic peak at 4 385 cm^-1 disappears. When these results are combined with those from XRD, it is determined that the LaAl₁₁O₁₈ phase is present. Samples 3^# and 4^# have characteristic Raman peaks from 3 564~3642 and 4 461~5 554 cm^-1, respectively. Upon combining the Raman peaks and XRD pattern for sample 2^#, a new LaAlO₃ phase is generated. The different ratios of the samples have little effect on the Raman peak intensity, and no new characteristic peaks appear. By enlarging the materials in steels that need targeted research, the evolution process of the modification of alumina powder after the addition of lanthanum oxide powder is analyzed. The research results can reference solving the problem of alumina inclusion modification during the actual steelmaking process.