Objective To study the pathogenesis of palpitation of unknown causes in patients with cardiac autonomic nervous function. Methods Forty-five patients with palpitations of unknown causes and 22 healty controls were examined for 24 hours of dynamic electrocardiogram parallel heart rate variability (HRV) analysis, comparison of palpitation group dynamic electrocardiogram almost normal with control group of 24 h normal R-R interval standard deviation ( SDNN ), each 5 min normal R-R interval mean standard deviation ( SDANN ), adjacent normal R-R interval difference of root mean square ( RMSSD ), SDNN<100 cases, SDNN ratio and LF/HF ratio and other indicators．Results Unexplained palpitation group and control group showed no significant difference in mean heart rate. In palpitation group ventricular arrhythmia was detected in 8 patients (17.8%), which was single source of ventricular extrasystole, averaged (83.2 ±119.3) / h; sinus heartbeat bradycardia in 3 cases (6.7%); paroxysmal supraventricular tachycardia of heartbeat in 6 cases (13.3%); dynamic electrocardiogram was normal in 28 cases (62.2%). Dynamic electrocardiograms were normal in control group (100%). In palpitation group, in addition to sinus bradycardia heartbeat, the SDNN and SDANN were smaller than that in the control group (P<0.05 or P<0.01), but the RMSSD. In palpitation group, dynamic electrocardiogram normal with SDNN<100 in 12 cases (42.9% ), in the control group 0 case ( 0%), the difference was statistically significant (χ²=12.4060, P<0.05 ). Compared with the control group, the SDNN circadian ratio and LF/HF ratio in palpitation group increased (t=4.280, 6.788, P<0.01). Conclusions In patients with palpitations of unknown causes, 24 h dynamic electrocardiogram is in majority generally normal, but heart rate variability analysis Results show that the cardiac autonomic function is damaged to varying degrees, mainly manifested as decrease in nocturnal vagus tone.