<p>Biological invasion has brought many problems and challenges to human life and ecosystem. In order to investigate the impacts of alien species invasions on omnivorous food web, a patch dynamic model was established to describe the patch occupancy of various species in omnivorous food web. Invasive species with different roles (omnivorous predator role or prey role preyed by two native species) are introduced into the omnivorous food web. The impacts of invasive species on omnivorous food webs and on each species in omnivorous food webs were studied under different habitat loss and habitat fragmentation degrees. The results show that: (1) When invasive species invade as omnivorous predators, the greater the trophic level gap at the invasive location, the more successful the invasion is, but this result is not obvious when invasive species play the role of prey preyed by two species. (2) With the increase of habitat loss and habitat fragmentation, it usually leads to the extinction of species, and the influence is stronger at higher trophic levels. (3) Habitat loss is detrimental to native and invasive species. However, the impact of habitat fragmentation on native species and invasive species is different. For invasive species, habitat fragmentation is not necessarily a bad phenomenon but may be beneficial to the invasion of invasive species, which mainly depends on the role of invasive species. The results of this study provide a new insight into species invasion and put forward some theoretical thinking on species invasion.</p>