Abstract: The soil arching effect is required to ensure the adjacent pertaining or anti-sliding piles to work safely and cost-efficiently in landslide engineering. However, the formation and destruction of soil arch is mainly determined by rational arrangement of pile spacing. Firstly, based on many studies on soil arching effects of piles, the skewback position, shape and axial equations of soil arch are analyzed to establish a rational soil arching model. Then, a formula for rational spacing between circular anti-slide piles is obtained combined with shear strength conditions on pile-soil interface and soil. Finally, based on an engineering project, the effects of several parameters on the rational pile spacing are analyzed, such as internal friction angle, parameters on the pile-soil interface and pile diameter. The result shows that the spacing increases with the increase of these parameters, whilst these effects will be weakened with the increasing landslide thrust.