Pharmacovigilance is important to monitor the safety of drugs. There are, however, problems with the quality of adverse drug reaction reports in China. This study aimed to analyze the quality of adverse drug reaction reports in China, identify the factors affecting it, and propose measures to improve it. In our study, the western province of Shaanxi, the central province of Hubei and the eastern province of Jiangsu were chosen as typical, and adverse drug reaction reports from these three provinces from 2015 to 2017 were systematically sampled. The sampling reports were scored and graded to assess their quality. The results showed that only 10.18% were considered high quality in a total of 3429 reports. There were statistically significant differences in quality by year, province, report type, report source, and occupation of the reporter (p < 0.001). Reports from Shaanxi were slightly poorer quality, and “new” and “serious” reports and those from pharmacists were higher quality. Five indicators were particularly poor quality: patient information, adverse drug reaction, reporter information, drug information and vigilance. In conclusion, the quality of adverse drug reaction reports in China still needs improvement. Factors affecting quality included timing, location, report type, report source, and reporter’s occupation. It may be helpful to publicize the importance of monitoring adverse drug reactions and improve the knowledge of reporters.