This is a multicenter, randomized, double-blind, placebo-controlled, parallel-group, phase 2 study. A total of 276 eligible Parkinson's disease participants with motor fluctuations will be enrolled and assigned to one of three cohorts. Within each cohort, participants will be randomized in a 3:1 ratio to receive either GM1 or matching placebo, resulting in six groups: Cohort 1 GM1 (n=69), Cohort 1 Placebo (n=23); Cohort 2 GM1 (n=69), Cohort 2 Placebo (n=23); Cohort 3 GM1 (n=69), Cohort 3 Placebo (n=23). All participants will continue their pre-enrollment anti-Parkinson's medication regimen as background therapy, which should remain as stable as possible during the study. The study consists of a 28-day screening period and an 85-day double-blind treatment period.

Inclusion Criteria:

1. Age ≥ 30 years at screening.
2. Clinical diagnosis of clinically established or clinically probable Parkinson's disease.
3. Currently receiving levodopa therapy (stable regimen for ≥4 weeks prior to randomization, with a levodopa equivalent daily dose ≥400 mg) and experiencing motor fluctuations (including wearing-off, on-off phenomena, etc.).
4. Hoehn-Yahr stage ≥2 in the "OFF" state.

Exclusion Criteria:

1. History or presence of other Parkinsonian syndromes or Parkinson-plus syndromes, or hereditary neurodegenerative disorders.
2. Diagnosis of Parkinson's disease dementia or severe cognitive impairment as judged by the investigator at screening.
3. Prior surgical treatment for Parkinson's disease or planned such surgery during the trial period.
4. History or presence of other neurological diseases.
5. History or presence of autoimmune diseases.
6. History or presence of any demyelinating diseases, including but not limited to acute inflammatory demyelinating polyneuropathy (Guillain-Barré syndrome).
7. History or presence of hereditary glycolipid metabolism disorders .
8. Known allergy to monosialotetrahexosylganglioside sodium or any excipient of the investigational product.