Objective:To investigate a brucellosis outbreak caused by contact with unquarantined sheep in Chongqing, and provide reference for prevention and control of brucellosis.Methods:In accordance with the requirements of the "Technical Plan of Brucellosis Prevention and Control Project of Chongqing" and the "Working Specification for Epidemic Disposal of Human Brucellosis" (DB50/T 946-2019), a self-designed brucellosis case questionnaire (version 2021) was used to carry out case investigation and laboratory tests on cases reported by medical institutions, and the data were analyzed descriptively.Results:According to "Working Specification for Epidemic Disposal of Human Brucellosis" (DB50/T 946-2019) in Chongqing, the brucellosis outbreak that occurred in December 2021 was determined to be a cluster outbreak, with a total of two confirmed cases of brucellosis, and a incidence rate of 2/9. The reason of the outbreak was the rearing and slaughtering of unquarantined sheep.Conclusion:We should strengthen the inspection and quarantine of livestock such as cattle and sheep, crack down on informal trade of livestock, and reduce the risk of brucellosis.