Abstract: Objective To observe the measurement errors in measuring blood pressure（BP） with automatic arm sphygmomanometer in the public places. Methods The process of BP measurement with automatic arm sphygmomanometer was observed in 213 subjects （52.8±13.8） years, 108 men, 105 women in the Second Affiliated Hospital of Nanchang University during February 2018. There were 7 common measurement errors:（1） the cuff tube was not placed 2-3 cm above the elbow;（2） inappropriate sitting posture;（3） the pretest rest time was less than 3 minutes;（4） BP was not remeasured 1 minute later;（5） wearing too many clothes（more than one layer of clothes）;（6） the sleeves rolled up, causing too much pressure on arms;（7） talking during BP measurement. Subsequently, participants were corrected for irregular measurements and asked to measure their BP again, finally 158 subjects measured their BP with automatic arm sphygmomanometer after the instruction. The BPs before and after the instruction were compared. Results Of 213 subjects, only 56（26.3%） had correct BP measurement. The most common error was that the cuff tube was not placed 2-3 cm above the elbow（84 cases, 39.4%）, the next error was that the pretest rest time less than 3 minutes（75 cases, 35.2%）, then wearing too many clothes（43 cases, 20.2%）. The systolic BP measured after the instruction was significantly lower than that of the before （131.9±20.5） vs（136.7±21.7） mmHg, t=5.421, P＜0.001. The diastolic BP tended to decrease after the instruction, but it was not statistically significant. Conclusion Measurement errors occurred in 73.7% of subjects who actively used automatic arm sphygmomanometer for self-BP measurements.