The definitive diagnosis of Parkinson's disease primarily relies on the patient's medical history, clinical manifestations, and a thorough physical examination by a neurologist. If the onset of the disease is very slow, presenting with symptoms such as bradykinesia and tremors, and the neurologist observes heightened muscle tone and slow movements during the examination, a high suspicion of this disease is warranted. Additionally, certain auxiliary tests are necessary, commonly including: First, testing the patient's sense of smell is crucial, as a reduced sense of smell is very important in diagnosing Parkinson's disease. Second, some brain MRI scans are needed mainly to exclude some secondary Parkinson's syndromes. Third, a brain PET-CT scan can be performed to examine the functionality of the striatum. Furthermore, an ultrasound of the substantia nigra in the midbrain can also be conducted, which holds significant value in assisting the diagnosis.