Sturgeon is one of the most important species of the Caspian Sea aquatics. Unfortunately, this species faces the threat of extinction today. This makes specific studies on any type of sturgeons more important than before. Studies like histological studies, radiology, and sonography, all require a complete understanding of the anatomy of this fish. Since pilot studies showed some misconceptions in description of the sturgeon digestive system, this study was conducted to evaluate more precise anatomical structure of the digestive system of Acipenser persicus as the most important sturgeon species of Iran.A total of 40 adult Acipenser persicus were used in this experiment. They were autopsied primary to the study. All parts of the digestive system from buccal cavity toward rectum and anal orifice were evaluated. The anatomical structure and relations of the different parts of the digestive system including oral cavity, pharynx, esophagus, glandular stomach, muscular stomach, pyloric process, small intestine, spiral intestine, rectum, liver and pancreas were described.The digestive tube is relatively short. The stomach has two parts. The first part, or the proventricle, is U-shaped. The second part or gizzard has thick muscles and is almost surrounded with liver lobes. Pyloric caecum is located on the left side bottom of the gizzard as a sponge like structure. The intestines are made of 3 parts: the small intestine, the spiral colon, and the rectum. The small intestine has two flexures that separate it to three parts named the descending, ascending, and the end part, respectively. The spiral colon is the longest part of the digestive tube. This part has mucosal spiral septum on the inner surface. The rectum is short and located in the middle of the abdominal cavity. However, in the present study the opening was shown to be located in the muscular stomach and the intestine junction, just close to the gall bladder duct opening.