Abstract: Based on the analysis of soil arch effect between adjacent anti-slide piles in some cutting slope projects, some control conditions are provided to calculate rational spacing between adjacent piles.These conditions are static equilibrium equation between slope thrust on the soil arch and resistance on its two end sections near the two piles, intensity principle of the point at internal edge of medial cross-section of the soil arch and intensity condition of two end sections of the soil arch. The rational calculation formula of spacing between adjacent piles is got. According to the formula, it is quantitatively shown that the spacing is increasing with increase of cohesion or internal friction angle of soil behind piles and decreasing with increase of slope thrust behind piles while other effective factors are not varying. In the end, the calculation procedure of spacing between adjacent piles is illustrated by a practical project and the result is rational.