The process of wheel compacted soil was simulated by using DEM. The results showed that after the compaction, soil hardness of different depths increased and changed obviously with depth. With the frequency increased, soil particle’s contact force increased and longitudinal influence domain deepened. When wheel passed in the first three times, the increasing trend of soil’s hardness was obvious. When wheel passed more than three times, the soil’s hardness also increased. But the increasing was not obvious. When the layer deep was 15cm, the hardness of compacted soil would increase by 155.2% when compared with the soil without compaction, the soil compacted six times would only increase by 22.9% when compared with the one compacted three times.