OBJECTIVE To observe the microanatomical structures of the wall of cavernous sinus (CS) in order to provide anatomical basis for direct microsurgical operation to the CS. METHODS 48 aides of the CS of adult cadavers were dissected in detail under operative microscope. RESULTS The CS was a narrow and long irregular hexahedron in shape. The supperior wall, the posterior wall and the superficial dural layer of the lateral wall of the CS were formed by internal layer of the cerebral dura. The deep layer of the interal wall was formed by the sheaths of nerves II, IV, V1, V2 with a reticular membrane between these sheaths. There was a superficial compartment between the superficial layer and deep layer of the lateral wall in 31.25% of the specimens. The inferior wall of the CS was intracranial periosteum. The medial wall was formed by stretched fibres from the tentorium of hypophysis. The anterior aspect was formed by the sphenoid sinus and the superior orbital fissure. Direct microsurgical approaches to the CS via the medial trangles of the superior wall and Parkinson tranales of the lateral wall were most important. CONCLUSION A microanatomical structure of the wall of the CS is provided for direct microsurgical operation to the CS, and the direct microsurgical approaches are discussed.