Objective:To discuss the characteristic trends of autonomic nervous system (ANS) activity in the processes of obstructive sleep apnea (OA) and central sleep apnea (CA). Methods:Thirty patients who were diagnosed as obstructive sleep apnea syndrome by polysomnograph were enrolled in the study. The RR intervals and relative data were extracted during the apnea,as well as a 15-second period before and after the apnea. The different trends of heart rate variability(HRV) for OA and CA were analyzed and compared. Results:HRV parameters varied significantly in the process of OA. The mean value,SD and rMSSD of RR intervals shifted slower level during OA,but returned to high level after OA. It suggested that RR interval was short during OA and with less variability. The HRV parameters showed no obvious changing in the process of CA. Conclusion:Different trends of ANS activity could be suggested during the processed of OA and CA. In other words,the sympathetic activity shifted to higher level during OA,and returned to a much lower level after it. In comparison,CA presented no significant change of ANS activity.