||Knowledge on species diversity in an area is often derived from samples. Studies have shown that plot designs influenced the number of observed species at local scale and species composition at landscape scale. However, species composition could vary at local scale, and the effects of plot designs on this has not been explicitly examined. Thus, the major objective was comparing species compositional similarity between different plot sizes and shapes at a sample location by simulation. Two 25-50 ha census plots from Taiwan and Peninsular Malaysia were used. A total of 15 combinations of plot sizes and plot shapes were simulated. Species compositional similarity between two plot designs was estimated by the Jaccard and Sørensen indices, and their abundance-adjusted counterparts. As plot size increased at a sample location, species compositional similarity between two plot sizes decreased due to more new species being observed. Decreasing plot compactness was found to sample different plant species composition, but plots with two different compactness could result in similar number of observed species. This study has explicitly studied effects of plot design in capturing local species composition, which has rarely been studied. A major conclusion is that two plot designs observing similar number of species do not necessarily imply similar species composition at local scale. Thus, sampling of plant diversity needs to consider species richness and composition in the same time at local scale.