Abstract: By transforming scientific research results into research-based undergraduate experimental teaching content, comprehensive experiments for the preparation and characterization of AlN films with different polarities were designed. The mix-polarity, N-polarity and Al-polarity AlN thin films are prepared by metal-organic chemical vapor deposition, and its surface morphology and crystalline quality are studied. The results show that when the graded AlGaN polarity control layer is introduced between the GaN and AlN epitaxial films, the AlN film is transformed into a single Al polar growth, and the half-peak widths of the high resolution X-ray diffraction rocking curves (002) and (102) are 375 arcsce and 420 arcsce respectively. This experiment stimulated the students’ interest in scientific research, in-depth study of the preparation and characterization methods of thin film materials, and cultivated students’ innovative and practical ability to actively explore.