Dissipative particle dynamics (DPD) is used to investigate the mesoscopic appearance and dynamic evolution process of polypropylene/polyamide 6 (PP/PA6) blends. The effect of PP-g-PA6 as a compatibilizer on the morphology of PP/PA6 under different mixing ratios were studied by adding proper amount of PP-g-PA6, and found that PP-g-PA6 can changed the mesoscopic morphology of PP/PA6 blends under a certain mixing ratio. Besides, 2%, 4%, 6%, 8% and 10% PP-g-PA6 were added to investigate the effect of different PP-g-PA6 on 90PP/10PA6 blends, respectively. The results showed that a small amount of PP-g-PA6 can reduce the interfacial tension and improve the compatibility, but too much PP-g-PA6 made the phase of PA6 swell and made the total interfacial tension of the system becomes larger, which was not good for phase fusion.