This study aims to evaluate the efficacy and safety of inhaled xenon for the treatment of children with autism spectrum disorder (ASD). The primary objective is to determine whether short-term inhalational xenon therapy can improve social functioning in children with ASD, as measured by changes in the Social Responsiveness Scale (SRS). Safety and tolerability of xenon inhalation in the pediatric population will also be assessed.

In this randomized, placebo-controlled trial, participants will receive either inhaled xenon or a placebo gas (medical air without xenon) to compare treatment effects.

Participants will:

Inhale 25% xenon or placebo for 10 minutes per day for 10 consecutive days Attend two clinical visits: one immediately after completion of the intervention and one at 3 months post-intervention for follow-up assessments and safety evaluations

Inclusion Criteria:

• Aged 4-18 years, with no gender restriction.
• Meeting the diagnostic criteria for Autism Spectrum Disorder (ASD) as specified in the Diagnostic and Statistical Manual of Mental Disorders (5th Edition) (DSM-5), with the diagnosis confirmed by assessment using the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2).
• The total T-score on the Social Responsiveness Scale, Second Edition (SRS-2) is ≥90.
• No treatment such as neuromodulation (transcranial magnetic stimulation, transcranial electrical stimulation) has been received for at least 1 month prior to randomization.
• For participants who have previously taken psychotropic medications prior to randomization, it is required that the medications have been discontinued for a minimum of 5 half-lives or 4 weeks, whichever is longer.
• The participants and their legal guardians confirm that they will not add new or alter the existing established treatment regimens such as behavioral rehabilitation during the study period.
• The legal guardians of the participants have a full understanding of the study content, participate voluntarily, and sign a written informed consent form.

Exclusion Criteria:

• Having other major neurological diseases (e.g., epilepsy, cerebral palsy), severe physical illnesses, or genetic syndromes.
• Having severe auditory or visual impairments that prevent the completion of assessments with cooperation.
• A history of anaphylaxis or adverse reactions to Xenon.
• Currently participating in or having participated in other interventional clinical trials within the recent 3 months.
• The investigator judges that there is any condition that may increase the risk to the participant or interfere with the conduct of the trial and the assessment of its results.