Abstract: According to the presumption of the interface stick-slip constitutive model and the fundamental principles of the shear displacement method, a theoretical formula for the critical loose pullout load of soil anchors and an inherent relationship formula between anchor pullout load and loose length are derived. The redistribution of anchor shear stress is caused by stick-slip properties of the interface, and the loading is transmitted to the remote end of anchorage system, which aggravates the deterioration of interior anchor. Based on the size relationship between interface shear strength and residual strength, the failure types of soil anchors can be divided into progressive and bursting ones. The discriminant criterion and the theoretical solution to the ultimate load in accordance with the failure of anchor pullout are proposed. Finally, based on the data of anchor pullout tests, the feasibility of the proposed method is verified through calculation and comparative analysis.