Objective To investigate the value of magnetic resonance imaging in the early diagnosis of PD by measuring the substantia nigra related sites in patients with Parkinson's disease (PD). Methods The conventional T2 weighted imaging(T2WI) was performed in 8 patients with PD and 8 normal healthy cases as the control groups by using 1.5T magnetic resonance imaging system, the width of substantia nigra compact(SNc), diameter of midbrain, mass of substantia nigra and signal value of substantia nigra were measured on T2WI, calculated the ratio of the width of SNc to the diameter of midbrain, compared the differences between PD patients and the normal control group, the Unified Parkingson's Disease Rating Scale(UPDRS) and the revised Hoehn-Yahr rating scale were used to assess the condition of PD patients, analysised the relationship between the width of SNc, diameter of midbrain, mass of substantia nigra, signal value of substantia nigra and the condition of PD patients. Results The width of SNc, ratio of the width of SNc and diameter of midbrain in PD group were lower than those in normal control group(P<0.05), but there was no difference in the diameter of midbrain, mass of substantia nigra, signal value of substantia nigra between PD patients and normal controls (P>0.05). The width of SNc, diameter of midbrain, ratio of the width of SNc and diameter of midbrain, mass of substantia nigra, signal value of substantia nigra in PD patients were not correlated with the condition of patients. Conclusion Magnetic resonance imaging is potential to be an ancillary method for PD.