Objective　To acquire the correct and accurate knowledge of carotid sheath by investiating the relationships between carotid sheath and cervical fascia.　Methods　20 adult cadavers (40 sides) were dissected. The posterior part of envelope fascia（superficial layer of cervical fascia）was dissected to observe whether it connected with carotid sheath, and to observe the characteristics of the connection. The relationships of carotid sheath to middle cervical fascia and superficial and deep layers of deep cervical fascia were observed. Meanwhile, the characteristics of connection were observed.　Results　Envelope fascia connected with carotid sheath loosely could be  separated easily by blunt dissection. Middle layer of the cervical fascia was composed of the junction of facial sheath of infrahyoid muscles, joining the anterior carotid sheath. Prevertebral fascia was composed of two parts, the superficial layer and deep layer, the former enveloping the carotid artery, jugular veinand vagus nerve, the latter not forming the carotid sheath. The junction fascia between middle layer of the cervical fascia and superficial layer of prevertebral fascia and carotid sheath was thick and tight.　Conclusion　Carotid sheath was closely associated with every layer of cervical fascia. Middle layer of the cervical fascia and superficial layer of prevertebral fascia forms the main body of carotid sheath.