Obstructive sleep apnea (OSA) is a common disease, the prevalence of which is increasing year by year, and the nocturnal intermittent hypoxia triggered by it is closely related to a variety of adverse health outcomes, therefore, exploring simple and reliable indicators for the assessment of nocturnal intermittent hypoxia has been a hotspot in recent years. In this paper, we summarise the different current methods of assessing indicators related to nocturnal intermittent hypoxia, including single assessment indexes characterising the frequency (oxygen desaturation index), duration (Time below 90% saturation, Saturation Impairment Time, etc.)、and magnitude (minimum of SpO2 values、magnitude of decrease in oxygen saturation, etc.) of intermittent hypoxaemia, and comprehensive assessment indexes (hypoxic burden, hypoxic burden index, hypoxic load, sleep breathing impairment index, etc.) and are reviewed.