Cervical spinal canal narrowing can lead to injury of the spinal cord and neurological symptoms including neck pain, headache, weakness and parasthesisas. According to previous and recent clinical researches, we investigated the geometric parameters of normal cervical spinal canal including the sagittal and transverse diameters as well as Torg ratio. The mean sagittal diameter of cervical spinal canal at C(1) to C(7) ranges from 15.33 mm to 20.46 mm, the mean transverse diameter at the same levels ranges from 24.45 mm to 27.00 mm and the mean value of Torg ratio is 0.96. With respect to narrow cervical spinal canal, the following charaterstics are found: firstly, extension of the cervical spine results in statistically significant stenosis as compared with the flexed or neutral positions; secondly, females sustain cervical spinal canal narrowing more easily than males; finally, the consistent narrowest cervical canal level is at C(4) for all ethnicity, but there is a slight variation in the sagittal diameter of cervical spinal stenosis (less than or equal to 14 mm in Whites, less than or equal to 12 mm in Japanese, less than or equal to 13.7 mm in Chinese). Narrow sagittal cervical canal diameter brings about an increased risk of neurological injuries in traumatic, degenerative and inflammatory conditions and is related with extension of cervical spine, gender, as well as ethnicity. It is hoped that this review will be helpful in diagnosing spinal cord and neurological injuries with the geometric parameters of cervical spine in the future.