Background: Heart RATE variability (HRV) represents the sympathetic nervous system activity induced by apnea or hypopnea events among OSAS patients. However, few studies have been conducted to clarify the association between HRV parameters and polysomnography (PSG) diagnostic indices. In our study, we postulate that the prevalence of cardiac arrhythmias is associated with OSAS, and HRV parameters may be an effective method for OSAS screening. Methods: Overall, 168 participants had been collected from 2011 to 2016 in the Second Affiliated Hospital of Soo-chow University. By apnea-hypopnea index (AHI), patients were sepaRATEd into three subsets: AHI < 5 as control group, 5≤ AHI<30 as mild-modeRATE OSAS group and AHI≥ 30as severe OSAS group. HRV and PSG parameters were collected based on electrocardiography and polysomnography system. CORRELATION analyses between standard deviation of R-R intervals (SDNN), SDNN index, RMSSD, PNN50, low frequency (LF), high frequency (HF) and LF/HF ratio and the AHI, ODI and MI were performed by Spearman's CORRELATION analysis. Results: Compared with control group (64. 5%) or mild-modeRATE OSAS group (67. 3%), the prevalence of arrhyth-mias was considerably greater in severe OSAS group (P<0. 05). Moreover, we demonstRATEd that LF/HF was greater in two OSAS groups than the normal group. Conclusion: CORRELATION analyses revealed a significant and positive relation between the LF/HF and AHI, ODI and MI in OSAS patients. Severe OSAS could be attributed to enhanced danger of incident arrhythmia. LF/HF ratio as a relevant feature may be an effective parameter for detecting OSAS.