The sieve bone belongs to the cranial bones of the brain and is one of the components of the skull base. The sieve bone can be divided into three parts, including the sieve plate, the vertical plate and the sieve labyrinth. In addition to the sieve bone, the cranial bones also include the paired parietal bones, temporal bones, and frontal bones, pterygoid bones, occipital bones, etc. 1, the sieve plate: a horizontal plate, separating the cranial cavity from the nasal cavity, there is an upwardly raised ridge of bone in the middle part of the plate, which is called the corona. There are many small holes on both sides of the corona, which are also called sieve holes; 2. Vertical plate: there is a downward-extending bony projection in the middle part of the sieve plate, which is called vertical plate, and the vertical plate is involved in constituting the bony nasal septum, which resides in the sagittal position; 3. Sieve labyrinth: the labyrinth of the sieve bone is on both sides of the vertical plate, and the outer part of the labyrinth is surrounded by thin bone fragments, which have a lot of gas-containing cavities, and the structure is also known as the sieve sinus. The medial wall of the labyrinth also contains two curved bony plates called the superior and middle turbinates. The lateral wall of the labyrinth forms the medial wall of the orbit and is also known as the orbital plate. Among the constituent structures of the sieve bones, the anatomical typing of the sieve sinuses is clinically important. The anterior sial sinus can be categorized into two types based on whether or not it encroaches outside the sieve bone; one is endosseous and the other is exosseous. When a patient needs endoscopic sieve sinus resection, if the sieve sinus is endosseous, the scope of surgery is limited to the sieve bone, and the safety of surgery is relatively high. In the case of the extra-sial type, the frontal sinus orbital roof sieve chamber needs to be opened during surgery, which is prone to intracranial and intra-orbital infections after surgery, and may lead to damage of orbital contents. Therefore, knowing the specific type of anterior sial sinus is also of great value and significance in choosing the surgical approach and determining the specific surgical scope.