Soil arching effect is the main load transfer mechanism of piled embankment. It is the key factor to analyze the load transfer and the settlement of piled embankment to correctly grasp the evolution mechanism of soil arch. Based on the model test of plane soil arching effect, the PFC2D software is used to establish the particle flow numerical analysis model of piled embankment, and the correctness of the numerical analysis model is verified by comparing with the test results. Firstly, the theoretical calculation formula for the height of inner arch and outer arch of plane soil arching is verified based on the numerical simulation results of particle flow under embankment self-weight stress. Then, the evolution law of soil arching effect in piled embankment under the external load on the embankment surface is analyzed from three aspects including the distribution of vertical stress in embankment, the variation of stress reduction ratio and the distribution of contact force in embankment. When the external load on the embankment surface increases from 10 kPa to 40 kPa, the soil arching in the piled embankment is stable. For the condition that the external load on the embankment surface increases from 40 kPa to 100 kPa, the soil arch structure in the piled embankment will degenerate and form a new soil arch structure, which shows that the vertical load carried by the subsoil presents an increasing trend.