Abstract: The appearances of the theory on optimized ecosystem functions caused by biodiversity, the view of ecological system functions dete rmined by component organism functions and the other non-tilting views have produced the diversified research results on the relation between ecological system functions and biodiversity. However, it is sure that the loss of key species impairs the functions of ecosystem. But for those structure-diversity ecosystems the key species can stabilize the ecosystem functi ons and to some extent mitigate the pressure triggered by species alteration. Studies on relations between stability of ecosystem and biodiversity have not achi eved an agreement, either. The common understanding between biodiversity and sta bility is that reduction in biodiversity can lead to a corresponding decrease in stability of ecosystem. However, there exists another different view asserting there is not any relation between stability and diversity. Through the comparison among researches on local diversity, regional diversity and global diversity and their corresponding measures of protection, we hold the view that the increase of biodiversity within different ranges can be achieved by providing local exper imental plots suitable for its reproductive condition for different species, by controlling regional biodiversity with small-sized species, and by all kinds of natural experimental methods.