Obstructive sleep apnea syndrome (OSAS), a pervasive disease, is closely associated with complications such as cardiovascular diseases, neurocognitive diseases, and metabolic syndromes. Continuous positive airway pressure (CPAP) is the standard treatment for OSAS, with low compliance due to multifarious factors. The two other modes of ventilation, bi-level positive airway pressure (BPAP) and autotitrating positive airway pressure (APAP), which were developed from CPAP, are slightly different from CPAP in specific groups, as well as the corresponding treatment effect and compliance. The compliance of traditional positional therapy is not high, but with the emergence of the neck-based position treatment device, its compliance and indications have changed. Although CPAP is superior to mandibular advancement device (MAD) in improving AHI, MAD seems to be comparable to CPAP in improving other indicators. Corticosteroids and leukotriene receptor antagonists are effective treatments for mild OSAS children. Whether corticosteroids can be used in other OSAS groups and their adjunctive functions to CPAP remains unclear. The combination of these two kinds of drugs appears to be more effective than single drug. Researches on transcutaneous electrical stimulation are still not enough. Its effectiveness and stimulation settings still need further study. This review summarized the various OSAS non-surgical treatments from indications, treatment outcomes, compliance, adverse reactions, and recent progress.