Abstract: Aimed at solving the problem of gravel soil landslide slip along the bedrock surface, the authors studied the formation of the soil arching effect and the load-bearing mechanism under the condition of parallel arrangement of three rows of micro combined anti-slide pile reinforcement and according to the model test and finite element analysis. The result reveals the optimum distance-to-diameter ratio. As the result shows，in a certain load, the soil arching effect is first formed at the first row of micro-piles, and then with the increase of distance-to-diameter ratio, the soil arching effect is gradually formed at the second and third row; furthermore, load sharing ratio in the front row is significantly greater than that of the rear one. Soil arching effect is inconspicuous or non-existent when the distance-to-diameter ratio is less than 3 or greater than 11. The most ideal distance-to-diameter ratio is 7 and 8.