Abstract: Forests under five different stand ages in four nature reserves and two eco-functional regions in Guangdong province were chosen as research objects. Total biomass, biomass of tree, biodiversity of tree and LAI were measured by field investigation. Its distribution characteristics and correlation were analyzed. The results showed that: The order of total biomass was: tree layer > shrub layer > herb layer, and the tree layer biomass of mature forest was significantly higher than others. The order of tree layer biomass was: mature forest > near mature forest > middle age forest > over mature forest > young forest, which showed a unimodal variation and reached a peak at mature forest stage. The tree layer LAI in the range of 0.77-4.19. The order of tree layer LAI was: middle age forest > mature forest > near mature forest > over mature forest > young forest, which showed an inverted "U" type change. There was a positive and significantly correlation between LAI and biomass in tree layer. LAI of middle age forest was significantly higher than that of young forest and mature forest. The differences of tree layer LAI between middle age forest, near mature forest and mature forest were not obvious. The order of Shannon-Winner index was: near mature forest > middle age forest > over mature forest > mature forest > young forest, which showed a "S" type change. The order of Pielou evenness index was: mature forest > near mature forest > middle age forest > over mature forest > the young forest, which showed a unimodal curve, and the peak in the mature forest stage. ShannonWinner index, Pielou evenness index of tree layer were positively related to tree layer biomass. Therefore, there were differences between biomass, species diversity index and leaf area index of tree layer in different age stands; there was a positive correlation between the biomass and species diversity index of tree layer; there was a positive correlation between leaf area index and biomass of tree layer.