Braided river delta is a common sedimentary system and a common oil and gas reservoir. Its sedimentary characteristics, sedimentary evolution process and internal structure have always been concerned by sedimentology research. Methods: An experimental braided river delta was simulated above a flat bedform. The sedimentary process and topography were recorded with a time- lapsed camera and a 3D laser scanner. Quantitively sedimentary process analysis was performed to investigate the sedimentary characteristics, evolution process and internal sedimentary architecture of the experimental braided river delta. Results: ① In the evolution of the braided river delta, its dimension, flow pattern, surface morphology and sediment distribution showed three stages of differences. ② In the initial stage, the braided river carried sediment directly into the “lake” and a lobe- shaped mouth bar was constructed. The water flowing into the lake does not have channelization characteristics. As the flower- shaped mouth bars gradually accumulated and emerged from the water surface, the delta plain was initially formed, and the river channels on the plain began to diverge, causing the subsequent mouth bars to transform into continuous arc- shaped bars distributed around the edge of the previous sedimentary body. The average radius of the delta increased rapidly at this stage. After entering the second stage, the growth rate of the average radius of the delta slows down, one or two main distributary channels and multiple secondary distributary channels were formed, and an arc- shaped lobe was formed in the river mouth area of the main channel. By the third stage, the area of the delta plain was larger, and its average radius growth rate was further reduced. The distributary channels on the plain were more bifurcated and smaller in width. Distributary channels were similar in scale and could transport sediments to the delta front at the same time. Deposition occurred in many parts of the delta edge, and multiple isolated small- scale mouth bars were formed in one run cycle. ③ During the whole process of sedimentary evolution, with the gradual increase of the scale of the delta, the width of the distributary channel gradually decreases, the flow path became longer, and the number of distributary channels gradually increased. The delta front deposits changed from a small number of arc- shaped continuous lobe to many isolated small- scale lobes. ④ In the second and third stages, the distributary channel showed multiple erosion- backfill autogenic evolution processes, forming multiple erosion- backfill complexes. ⑤ The fore- sets of braided river deltas have the characteristics of gradually weakening sedimentary continuity and gradually complex superposition rules from bottom to top and from proximal to distal parts. Conclusions: Flume experiments reveal the sedimentary evolution process and internal architecture of braided river deltas, which can provide a reference for outcrop anatomy and subsurface reservoir research.