Inclusion Criteria:

1. A physician-diagnosed SCA3 according to diagnostic criteria, with definite clinical symptoms and confirmed genetic testing;
2. Age 18-75 years;
3. Baseline total score of SARA: 8-30 points (inclusive); SARA gait function subscore: 2-6 points (inclusive);
4. Willing to participate and provide informed consent;
5. Have a reliable caregiver available;
6. No severe cognitive impairment that would preclude reliable reporting of adverse events or efficacy during treatment.

Exclusion Criteria:

1. History of seizures or convulsions, or a seizure within 6 months prior to enrolment;
2. History of severe traumatic brain injury or intracranial neurosurgery;
3. Presence of cardiac pacemakers, cochlear implants, intracranial implanted electronic devices, or other MRI-contraindicated ferromagnetic implants;
4. Severe cognitive impairment (Mini-Mental State Examination [MMSE] score ≤ 9) or severe visual, auditory, or speech dysfunction preventing cooperation with scale assessments and study procedures;
5. Pregnant or lactating women, or women of childbearing age not using reliable contraception;
6. Previous neuromodulation treatment (e.g., rTMS or tDCS) within the past year;
7. Skin breakdown or inflammation at the electrode placement site, or known allergy to conductive gel or electrode patch adhesives;
8. Currently participating in other interventional clinical trials, or planning to participate in other trials that might affect the outcome assessment of this study during the study period.