Objective To analyze the spectrum and characteristics of common diseases in Chinese escort navy fleets in Aden Gulf, providing references for optimizing the allocation of medical resources and improving the efficiency of medical service. Methods A total of 3 068 navy soldiers who served in four escort missions between 2013 and 2016 in Aden Gulf were included in the present study, and they were marked as batch A, B, C and D according to the task sequence. The records of outpatient and emergency departments, data from weekly medical report and data from summary of health service were collected for analyzing the circadian disease incidence, morbidity per day and the composition of diseases. Results The incidence of diseases took a declining tendency from the beginning to the end of the mission. The latter two escort fleets had a significantly lower morbidity per day than the former two escort fleets (P<0.05). The incidence rates of the top six diseases were respiratory infection, gastrointestinal inflammation, trauma, neck lumbar spinal joint diseases, skin tinea and periodontal inflammation in the four fleets. However, significant differences were found for the composition of the top four diseases among different escort fleets (P<0.05). The incidence of insomnia kept steady in four batches of fleets (P>0.05). Conclusion With the normalization of the escort missions, the morbidity per day of the escort soldiers declines in the later escort fleets. More attention should be given to improve the sleeping quality and reduce the occurrence of insomnia while still keeping an eye on common diseases.