Aim: This study was conducted to provide data on weed species composition and biodiversity indexes at different rice crops inside and outside of the dike system in An Giang province, Vietnam. Methodology: Weeds were collected from paddy rice of inner and outer side of dike system from six districts of An Giang province, Vietnam. From each 2 sampling sites, two quadrats with 100 m (10 m × 10 m) per quadrat were selected to collect weed after 75-80 days of rice planting. Weeds were collected and identified for their scientific name, and the number of each species was defined, followed by calculation of the occurrence frequency and density of samples. Biodiversity indices viz. Shannon-Weaver (H’), Simpson (1- λ), Margalef (d), and similarity index were also studied among three crops and two sides of dike system. Results: Interpretation: The weed composition in the paddy rice in An Giang was diversity with 137 species. Among them, the most species belonged to families Poaceae, Cyperaceae, and Compositae. The species composition of Crop 3 was the highest one. Species occurrence frequency and weed density of groups C, D, E reached the highest value in Crop 1, followed by Crop 2 and 3. The biodiversity indices of weed species composition in the studied sites were high, reaching the highest value in Crop 3. Interpretation: The results of this study enhance the knowledge of weed species composition and biodiversity indexes to effectively manage and control weeds in rice cultivation.