OBJECTIVE： To observe the effects of penehyclidine hydrochloride on heart rate and heart rhythm variability （HRV） during cardiac CT angiography （CTA）. METHODS： 70 subjects undergoing CTA in our hospital were randomly divided into control group and observation group， with 35 cases in each group. Observation group was given Penehyclidine hydrochloride injection 0.8 mg，ivgtt， and then given other 0.5 mg if therapy failure within 30 min； control group was given Metoprolol tartrate tablet 50 mg，po， and then given other 20 mg if therapy failure within 30 min. Heart rate of ECG and DCG， heart rhythm variation power index， HRV time domain parameter， heart rhythm variation， the occurrence of ADR were observed in 2 groups. RESULTS： Before medication， there was no statistical significance in above indexes （P＞0.05）. The routine electrocardiogram 1， 5， 10 min after medication and heart rate monitored by DCG 1， 5， 10， 20 min after medication in observation group were significantly lower than in control group， total power （TP）， low frequency （LF） and high frequency （HF） of heart rhythm variation 5， 10， 20 min after medication in observation group were significantly betrer than control group， with statistical significance （P＜0.05）. The changes of HRV time domain parameter in observation group were significantly increased compared to control group， the time of heart rate reaching 70 time/min in observation group was significantly shortened， compared to control group except for average standard deviation of 5 min autonomic nerves or tenth nerves during sinus RR period； the times of heart rate fluctuation in observation group was significantly less than in control group during CTA， and successful rate was significantly higher than control group， with statistical significance （P＜0.05）. No obvious ADR was found in 2 groups after medication. CONCLUSIONS： Penehyclidine hydrochloride can significantly slow heart rate down， have short time of heart rate control， long maintenance time and slight heart rate fluctuation， and can be used in CTA with good safety.