Biological invasions have received considerable attention in recent years because of their increasing impacts on native ecosystems and economics. In invasion ecology, the relationship between biodiversity and exotic species invasion has long been hot spot of community invasibility. Elton′s classic hypothesis, supported by theory, experiment, and anecdotal evidence, suggests that an important determinant of invasion success is resident biodiversity. It considers that high diversity enhances community competition and makes them more difficult to be invaded. However, the observational results of recent experiments and models have led to many more questions about this hypothesis so that a variety of hypotheses are thus brought forward. Then what is the relationship between diversity and biological invasions? In this paper, six scenes in two different communities are designed to test invasion mechanism under the two conditions of different biodiversity and the same biodiversity. The results show that the two communities respond differently to biological invasions in the scenes of the same diversity. The alien species could invade successfully the geometric community but is excluded out of the multiple community. That may be the result of available resources fluctuation, which consents to Resource Opportunity Hypothesis proposed by Davis. Under the conditions of the same biodiversity, due to the special structure of the multiple community, its resources′ occupancy rate is far greater than that of the geometric community. Therefore, the geometric community is more likely to be invaded by non-native species. When the biodiversity is different, it is hard to tell whether the invasion of alien species is determined either by diversity or by remaining resources.