Abstract: The design codes for screw anchor piles have shortcomings in calculation of the horizontal drawing capacity, and the understanding of soil pressure distribution on the anchorage surface is not unified in theoretical researches. A self-made large test sand box is used to carry out the horizontal drawing model tests on a single screw anchor pile. The soil pressures on the upper and lower surfaces of the anchor blade are directly measured to analyze the distribution rules. The displacement-related method is introduced to approximatively calculate the soil pressures, and based on the p-y curve of lateral resistance, a horizontal drawing mechanical model for the single screw anchor pile in sand is established, and the displacement-related theory is deduced to calculate the horizontal bearing capacity at last. The results show that in the horizontal drawing process, the soil pressure distribution on the surface of the anchor has non-linear relationship with the distance from the measuring point to the cental axis of the anchor, and the displacement should be considered in the calculation of soil pressures. The mechanical model and displacement-related capacity theory based on the mechanical equilibrium analysis have good effectiveness in the comparision validation. For the normally used single screw anchor pile (diameter ratio of bar to anchor d/D≤5), when the burried depth ratio is greater than 4, the horizontal capacity can be calculated according to the equal diameter naked pile directly, neglecting the effects of anchors.