China has a huge population with respiratory diseases, these diseases should be managed well in primary care, however, primary care physicians' knowledge level of these diseases were unknown. The aim of the study was to assess primary care physicians' knowledge of asthma, CAP, COPD, and influenza in China. An e-questionnaire was distributed to attendees of respiratory diseases academic conferences in China from July, 2017 to December, 2018. 7391 questionnaires were returned and 4815 valid questionnaires were analyzed, 3802 (79.0%) from community health service centers and 1013 (21.0%) from township hospitals. The average score of the questionnaire was 83.3 (+/- 20.397) and 72.1 (+/- 20.898) in township and community hospitals, respectively (P < 0.05). 61.4%, 48.7%, and 42.5% of the primary care physicians were aware of clinical manifestations of COPD, asthma, and simple influenza. 85.7%, 8.1%, 16.1%, and 1.0% knew how to diagnose COPD, asthma, CAP and influenza, respectively. 94.4% of the physicians lacked the knowledge of treating COPD with bronchodilators; 53.7% knew non-pharmacological treatments for COPD. 73.6% were unable to deal with asthma attacks. 65.1% did not know what the most essential and important treatment for influenza was. 92% of physicians did not know the management for stable COPD; 3.0% knew all prevention and management measures for asthma. 37.9% knew all the preventive measures for CAP. 44.9% did not know the important role of influenza vaccine in preventing influenza and its complications. Primary care physicians in China had a poor knowledge of CAP, asthma, Influenza, COPD. There is a need for improved training of common respiratory diseases.