Abstract: An outbreak of paratyphoid fever epidemic occurred in Yuanjiang county of Yunnan province between April 2010 and August 2011, with 587 cases diagnosed as paratyphoid fever A. Relevant institutions conducted a field study to analyze distribution characteristics of the cases, environment monitoring, management of contact persons, disposition of epidemic region, and the reporting of the epidemic. Specimens from the cases and environment of epidemic region were detected for isolation and identification of pathogens with molecular typing and genomics technique simultaneously to trace infectious source of the epidemic. The investigation findings demonstrated that the epidemic was related to some imported cases and that the pathogen-contaminated irrigation water polluted vegetables planted and the infection might caused by eating of uncooked vegetables by the cases; the findings also suggested a infectious source-sewage-contaminated vegetable-population transmission cycle. The epidemic subsided 17 months after the implementation of targeted measures including environment contamination control, diagnose and treatment of the cases, management of the contacts, and health education among the public. The results indicated that molecular typing and infectious tracing with genomics technique could play an important role in precision control of paratyphoid fever epidemic.