Through the indoor model test, using the visual tracking technology, through observing the soil displacement field of anchor in the drawing process, and the soil particle porosity and particle trajectory tracking, and then the mechanism of anchor and soil nail is studied. The study found that the particles in the process of pulling anchor for the shear effect of the soil particles move to the soil nailing mobile, but because the boundary constraint of soil nail, the particles reverse, the final compaction zone is formed between the anchor and the soil nailing; the formation of compaction zone not only decreases the soil displacement, but also make the limit of soil nailing, and anchor pullout capacity is improved, which explains why the anchor composite soil nailing can decrease the soil displacement. The study results can provide a theoretical basis for the design of and construction of the anchor composite soil nailing.