Coronavirus disease 2019 (COVID-19) epidemic is the most widespread global pandemic in the past 100 years. Person-to-person transmission of COVID-19 infection leads to the major threat of human safety and health. At 00:00 on January 24th, 2020, Tianjin City launched the first-level response to the COVID-19 epidemic. At 18:00 on the same day, Management Committee of Dongjiang Free Trade Port Zone of Tianjin received areport that there were 15 people who had fever on the Costa Crociere carrying 4 806 people from Japan back to the home port of Tianjin Dongjiang Cruise. At the same time, there are more than 140 Chinese Hubei tourists. Tianjin Municipal Committee and Government, Tianjin Customs, Binhai New Area District Committee Government, Tianjin Health Commission, Tianjin Binhai New Area Health Commission formed an emergency command center immediately to deal with the epidemic comprehensively. At 06:40 on January 25th, 2020, the medical investigation team made up by Tianjin Binhai New Area Health Commission and Tianjin East Administration of Customs boarded the cruise ship. With reference to the customs inspection and quarantine regulations, in accordance with the Diagnosis and treatment of pneumonia caused by novel coronavirus (trial version 3) for mulated by the National Health Commission of the People's Republic of China and the Novel coronavirus infected pneumonia port control and technology plan (first version) formulated by the General Administration of Customs, combined with the actual situation of cruise ships, the medical investigation team developed the inspection standards, including door-to-door inspections, temperature measurement and epidemiological investigations on all persons on board of the cruise ship. A total of 4 806 person-times were investigated in the affected area, including 3 706 tourists and 1 100 crew members. Seventeen people at high risk of COVID-19 were identified, including three Wuhan tourists. The reports of 2019 novel coronavirus (2019-nCoV) nucleic acid detection on throat swab samples for those who were identified as high risk were returned as all negative at 14:54 on the same day. At 19:30, the medical investigation team completed the investigation and evacuated the cruise ship. The temperature measurement, medical observation and resettlement of passenger were handed over to relevant personnel. After 2 weeks, the follow-up result of 2019-nCoV nucleic acid of 17 high risk people were all negative. The overall command and comprehensive coordination of the onshore command center together with the rigid principles and excellent responds ability of the on-site epidemic investigation team ensured the successful completion of the epidemic investigation work, and also provided reference for further improving the management and disposal capacity of public health emergencies at sea.