Niche and interspecific associations, which are significant quantitative and structural characteristics, reflect relationships among species in a plant community as well as community stability, and thus providing an important theoretical basis for forest vegetation restoration and reconstruction, forest management and biodiversity conservation. In order to understand mechanisms underlying the formation of niche and interspecific associations of main species in the shrub layer of Cyclobalanopsis glauca communities, a total of 100 shrub plots were established and investigated in the Cyclobalanopsis glauca communities in karst hills of Guilin. We selected 20 shrub layer species on the basis of their importance values. The niche characteristics of main species in shrub layers were quantified with the indices of Levins niche breadth, Shannon niche breadth, Schoener niche similarity and Pianka niche overlap. The interspecific association was researched by using a set of methods, namely, variance ratio(VR), χ² test, Pearson's correlation test and Spearman's rank correlation test. The results showed that:(1)the Levins and Shannon niche breadth index indicated that the niche breadth of Cyclobalanopsis glauca was the largest among the twenty species that we have studied. It indicated that Cyclobalanopsis glauca had a stronger ability to compete and utilize resources in the shrub layer, with the absolute competitive advantage and stronger ecological adaptability. The species with larger importance values generally had larger niche breadth, but the rank orders of them were not exactly the same. (2)the mean value of niche similarity of main species in the shrub layer was 0.156. There was a lower degree of niche similarity among species within the community, indicating that they had a lower similarity in resource utilization. (3)the result of niche similarity proportion and niche overlap was similar but not the same. The differences between them suggest that using similar resources are not sufficient to cause competition among these species. (4)the W test showed that the overall interspecific associations were significantly positive associations among the main species in the shrub layer. This reflected that the Cyclobalanopsis glauca community in karst hills of Guilin was in a relatively stable succession status. (5)the results of the χ² test, Pearson's correlation test, and Spearman's rank correlation test showed that the significance ratios of the species pairs were all lower. The species pairs with insignificant interspecies correlations accounted for the majority of the species pairs in the shrub layer, reflecting a weak association among the various species pairs in the shrub layer. Most of the species showed an independent distribution pattern. (6)both Pearson's correlation coefficient and Spearman's rank correlation coefficient showed significantly positive correlations with niche similarity and niche overlap value. In other words, the species pairs with stronger positive association generally had larger niche similarity and niche overlap. On the contrary, the species pairs with stronger negative association generally had smaller niche similarity and niche overlap.