This experiment mainly studies the interference diffraction phenomenon of two kinds of complex structures. One is to use the hexagonal structure of the watch strap to carry out the interference diffraction experiment of light. By changing the distance between the light source and the hexagon, and the position of the receiving screen to observe the diffraction phenomenon, it is found that the hexagonal interference diffraction phenomenon is obvious, and the distance is an important parameter affecting the interference phenomenon. At the same time, we set up a set of instruments that conform to Kirchhoff diffraction. Using Kirchhoff theory, the relative intensity diffraction formula of diffraction of complex structure-hexagonal-like holes on the screen is derived, and the instrument is used to simulate different incident angles. Different diffraction patterns find out the internal laws between them.