The condensation of nanoparticles, the holes of porous materials, and the morphology of quasi-crystals are difficult to describe the teaching of solid state physics. Therefore，the experiment on the fractal structure is introduced into the process of teaching for the visual presentation. Based on a simple experiment on finger fractal, the fractal structures and dimensions that a mixture of ink and alcohol on the diluted acrylic paint are investigated. By changing the ratio of ink and alcohol in mixture and concentration of acrylic paint, the factors affecting the fractal structure of fingers are obtained, including the applied electric field and temperature, which is helpful for students to understand the fractal theory. Lastly, the growth of dendritic crystal is simulated based on COMSOL software, which shows that the fractal structure is related to anisotropy and dimensionless latent heat. The introduction of interesting experiment, will be help for cultivating students' innovation awareness and self-investigation ability, which is an important link of practice teaching under the background of new engineering.