To clarify the causal factors of a case with severe Chlamydia psittaci pneumonia in Jiujiang District， Jiangxi Province and provide a scientific basis for effective prevention and control. Basic information and epidemiological data of the case were collected by epidemiological survey， and the samples from the close contacts and environment were collected for pathogen detection. A 37-year-old female patient was admitted to the hospital due to "fever with cough for five days and worsening dyspnea". The results of targeted next-generation sequencing （tNGS） of pathogenic microorganisms in the bronchoalveolar lavage fluid of the case indicated that the patient was infected with Chlamydia psittaci. Our epidemiological investigation revealed a clear history of chicken and duck exposure. Four throat swab samples of close contacts and one spleen， liver and lung sample of sick chicken and duck were collected for testing. One of the duck tissue samples tested positive， while the other samples were negative. The severe pneumonia was likely caused by exposure to the external environment contaminated by Chlamydia psittaci. Poultry farming should be regulated to prevent the transmission infection from poultry to humans．Additionally， awareness among medical staff should be increased to prevent severe outcomes．