Objective To investigate two different doses atropine make reverse effects on the function of sinus node and the atrioventricular node inhibiting action dexmedetomidine (Dex). Methods 20 healthy volunteers were included in the clinical trials aged 18~30 years (12 male, 8 female). The volunteers were administered with Dex at loading dose 1.5±0.5 μg/kg and then at 0.75±0.25 μg/(kg·h). During the trail, the volunteers who happened the minimal heart rate less than 50±5 bpm, atrioventricular node forward 2∶1 block point less than 150 bpm needed to randomly accept 0.5 mg(group A₁)or 1 mg(group A₂)atropine to antagonize(n=10). SNRT, CSNRT, AVN 2∶1 block point and AVNERP were recorded through TELAP. Results Intra-group comparison indicated functional parameters of SN and AVN were inhibited by Dexsat T₁. SNRT were prolonged (P<0.05), AVN 2∶1 block point were decreased (P<0.05),AVNERP were prolonged at T₁ compared with T₀(P<0.05). All indexes in group A₁ and AVNERP in group A₂ were back to basal level after using atropine at T₂(P<0.05). SNRT, CSNRT were shorted at T₂ compared with T₀ in group A₂(P<0.05). AVN 2∶1 block point had more increased at T₂ compared with T₀ in group A2(P<0.05). Inter-group comparison indicated no significant differences in functional parameters of SN、AVN at T₀(P>0.05). SNRT, AVNERP were shorted at T₂ in group A₂ compared with group A₁. AVN 2∶1 block point were increased at T2 in group A₂ compared with group A₁. Conclusion 0.5 mg atropine may reverse the function of SN and AVN that are inhibited by Dex. 1 mg atropine may increase functions of SN and AVN that are inhibited by Dex.