Objective To investigate whether increased signal intensity (ISI) can help assess the prognosis in patients with cervical spondylotic myelopathy (CSM) by means of measuring the ratio of signal intensity. Methods A retrospective study with two or more years follow-up of 57 patients with CSM underwent posterior cervical decompression were carried out from February 2000 to February 2006. 1.5T MRI was performed in all patients before surgery. T2-weighted images (T2WI) of sagittal ISI on the cervical spinal cord were obtained, For those with ISI, the values of signal intensity of the spinal cord on T2-weighted image (T2Wl) and TI-weighted image (TIWI) of sagittal view were measured at the location where there was ISI on T2WI, and the ratio of signal intensity of T2WI / T1WI (T2/T1 ratio) at the same level of the spinal cord and with similar area was calculated on the computer. Patients with ISI were subdivided into 2 groups according to T2/T1 ratio. Results ISI was not observed in 20 patients (group 1). The range of T2/T1 ratio of other 37 patients was from 1.28 to 2.80 and the median was 1.65. Nineteen patients were divided into group 2 (ratio range, 1.28-1.63), and 18 into group 3 (ratio range, 1.67-2.80). Significant differences were noted in age at surgery, duration of disease, recovery rate, pre and preoperative JOA score among three different groups.Spearman's rank correlation showed that T2/T1 ratio was positively correlated with age at surgery and duration of disease, negatively with pre- and postoperative JOA score and recovery rate. Conclusion Patients with ISI and higher T2/T1 ratio tend to have relatively severe preoperative state of illness and poor prognosis after surgical intervention. Spinal cord signal intensity change on T2-weighted MRI might be a predictor of a poor outcome in terms of functional recovery rate in patients underwent operations for multi-level CSM.