To estimate temporal change of regional tree diversity in Xishuangbanna, Southwest China, for this, we selected sampling plots from four forest vegetation types through field survey, including tropical rainforest(TRF), tropical seasonal moist forest(TSMF), tropical lower montane evergreen broad-leaved forest(TEBF)and tropical coniferous forest(COF). We used remote sensing imageries to map the distribution of four forest vegetation types for four different time periods 1992, 2000, 2009, 2016. Evenness indices of Simpson, Shannon-Wiener and Scaling were used to compare the tree evenness difference among the four forest vegetation types. Scaling index and grey correlational evaluation model were used to measure the biodiversity change in Xishuangbanna in four periods. The results were as follows:(1)Forest area showed a decreasing trend during 1992 to 2009 and then increasing to 2016, proportion of changing forest area found to be 65.5% in 1992 decreasing to 53.42% in 2000, then kept 52.49% in 2009 and increasing to 54.73% in 2016, but TRF area showed a decreasing trend during 1992 to 2016.(2)Four forest vegetation types had a significant difference that contributes to biodiversity, the tree evenness of four forest vegetation types were in the order TRF> TEBF> COF> TSMF, the richness of four forest vegetation types were in the order TRF> TEBF> TSMF> COF, this sorting of vegetation's contributions to Xishuangbanna tree diversity was TRF> TEBF> TSMF> COF.(3)Tree diversity of TRF and TSMF showed a decreasing trend from 1992 to 2016, the tree diversity of Xishuangbanna forest vegetation in different time periods were sorted as 1992>2009>2016>2000. The present study indicates that economic activity is an important factor to affect the regional diversity in Xishuangbanna, and the conservation of tropical rainforest has a great significance in maintaining biodiversity in Xishuangbanna. [ABSTRACT FROM AUTHOR]