Abstract: Based on the deformation coordination between the anchorage body and surrounding soil in the elastic-plastic state, a model for load transfer mechanism of anchor bars under the confining pressure was constructed, and the theoretical calculation formulas among external loads, the plastic radius of soil strata embedded in anchor rods and ultimate pull-out forces of anchor rods were deduced. The influence of the coarse particle content, stress state of anchorage bodies and water content of soil on the ultimate drawing forces of anchorage rods in soil strata was analyzed by pull-out tests. The results showed that to improve the stress state of soil strata where anchor rods were embedded in a certain range was beneficial to prevent anchor rods from being pulled out of the soil. When the coarse particle content of the soil was 60%, the soil was relatively denser, the stress in the soil particles was relatively more uniform during being pulled out of anchor rods, and the bearing capacity of the anchor rods was relatively higher. Under the same confining pressure, the ultimate drawing forces of anchor bolts in soil increased first and then decreased with the increase of the water content. In addition, the theoretical calculation values of ultimate drawing forces were in good agreement with the test results, the validity of the theoretical model was verified.