In order to analyze the change of vegetation and species diversity in Mt. Tashan from 1959 to 2009, we conducted a field botanical investigation using system method and typical sampling method between 2009 and 2010. At the present, the main vegetation type in Mt. Tashan is Pinus thunbergii forest-P. tabulaeformis forest-Pinus thunbergii forest. The regional vegetation became mixed coniferous forest(Pinus thunbergii forest, P. densiflora forest and P. tabulaeformis forest)-deciduous broadleaved forest(Quercus variabilis forest and Q. acutissima forest), which replaced single coniferous forest(Pinus thunbergii forest), and many coniferous forest into broadleaved forest within 50 years. It's obvious that coniferous forest was successive to broadleaved forest. It's showed the species richness in Mt. Tashan is the herb layer > the shrub layer> the arbor layer. The global regularity of Shannon-wiener index and Simpson index were the shrub layer > herb layer > arbor layer. Both the species richness and the diversity index are lower, and so it was still in the early forest successive phase.