The spatial distribution pattern and scale effect of species diversity are the core issues of community ecology. However, how the spatial variation and scale effect of species diversity change over time remains unclear. The karst seasonal rain forest in Southwest Guangxi is one of the hot spots of global biodiversity. Based on long-term monitoring data, this study systematically analyzed the multi-scale variation and temporal dynamics of species richness, abundance, Shannon-Weiner index, Simpson index and Pielou evenness index in a 15 hm² northern tropical karst seasonal rainforest in Nonggang, Guangxi aiming to provide a basis for biodiversity conservation and utilization in this region. The results showed that: (1) The spatial distribution of species diversity showed high spatial heterogeneity, and the diversity of different habitats varied greatly across habitats and scales; (2) The spatial variability of diversity indices was significantly scale-dependent: the variance of species abundance and richness increased with sampling scale, while the variances of the Shannon-Weiner, Simpson, and Pielou indices decreased monotonically. The coefficient of variation of diversity also showed a linear decrease with scale; (3) Temporal dynamics analysis from 2011 to 2021 revealed distinct variation patterns among diversity indices: the variances of abundance and richness exhibited significant downward trends, whereas the variances of the Shannon-Weiner, Simpson, and Pielou indices increased significantly; The coefficient of variation of richness remained stable over time, while that of the other diversity indices increased significantly overall, with no significant changes during the later period (2016-2021). The above research results showed that the species diversity of karst seasonal rainforest had complex temporal and spatial variation characteristics, and the scaling interpretation should be carried out carefully. They also highlighted the importance of multi-scale integration and long-term monitoring for optimizing karst biodiversity conservation strategies.