It is necessary to understand the bending moment distribution law of each surrounding pile, especially under the dynamic load of train, when the surrounding pile-soil arch chord coupling anti-sliding structure (SPSC-AC anti-sliding structure) is used in the control design of creep of high speed railway subgrade. Based on the study of creep mechanism and deformation characteristics of subgrade in a bridge-tunnel transition section of the express railway, a three-dimensional numerical model of subgrade creep protected by SPSC-AC anti-slide structure was established by using Midas/GTS NX,and the non -linear dynamic time course + finite element strength reduction method is adopted to analyse the governing effect of the SPSC-AC anti-slid structure and explore the bending moment characteristics and distribution of the SPSC-AC anti-sliding structure under the dynamic load of different train speeds，and suggesting optimisations.The result shows: Spacing 4d arrangement of main control surrounding piles of the SPSC-AC anti-sliding structure, The distribution of bending moment value of each surrounding pile is roughly in the shape of inverse S; At a certain speed, the variation of the maximum bending moment of each surrounding pile with time is basically the same, showing the shape of "simple harmonic"; With the increase of train speed, the bending moment of surrounding pile in stable stage also increases;At a certain speed, the bending moment of each surrounding pile in the stability stage is No.1 pile ＞ No.3 pile ＞ No.2 pile ＞ No.8 pile ＞ No.4 pile ＞ No.7 pile ＞ No.5 pile＞No.6 pile ; The bending moment distribution ratio of each enclosure pile is 1.00 for No.1 pile, 0.51 for No.3 pile, 0.46 for No.2 pile, 0.46 for No.8 pile, 0.46 for No.4 pile, 0.33 for No.7 pile, 0.31 for No.5 pile and 0.29 for No.6 pile. The research results can provide a basis for the engineering control design of subgrade creep prevention of high-speed railway.