Research conclusions:(1)The collapse risk of the soil between piles can be effectively reduced by building a certain amount of anchor arms between the piles. The anchor arms can tightly connect the unstable soil between piles. The soil is compacted by soil arching for stabilizing the real soil. The compacted soil around the soil arching cycle plays a role of anchoring section.(2)The results of numerical analysis show that anchor should be arranged in the proper position with more density between the two adjacent cantilever piles because of the geometric influence of the soil arching effect between piles. This arrangement can produce a better reinforcement effect than the uniform arrangement.(3)The drilling depth of the pile anchor can be designed like this: the upper is shorter and the lower is properly longer, however, the drilling depth should not exceed 1 .5 times of the spacing between piles. If the lower part of the soil between piles is rather compacted，reduction of the drilling depth of the small anchor arm can be considered.(4)Most of reinforcing the soil between pile with anchor arm are used for further improving the stability of piles and soil and reducing the risk of road operation caused by the soil collapse and dropping between piles，or for beautifying the environment around the road.