To analyze the epidemiological characteristics and diagnosis of imported malaria before and after the COVID-19 pandemic in Nanjing City, data pertaining to the epidemic situation and case investigation of malaria in Nanjing City from 2017 to 2022 were collected from the National Notifiable Communicable Disease Reporting System to analyze the source of infection, distribution and diagnosis and treatment of malaria reported cases. A total of 89 malaria cases were reported in Nanjing City from 2017 to 2022, and all were imported cases. Among them, falciparum malaria accounted for 79.8% (71/89). A total of 71 and 18 malaria cases were reported before and after COVID-19 epidemic, respectively, and falciparum malaria accounted for the highest proportion before (78.9%, 56/71) and after the epidemic (15/18). The reported cases mainly acquired Plasmodium infections in African regions， with accounted for 94.4% (67/71) before and 18/18 after the epidemic. The reported cases were distributed in each month from 2017 to 2019, and the number of reported cases peaked in January (12 cases). There were no significant seasonal variations in the distribution of reported malaria cases from 2020 to 2022. The number of reported cases peaked in November (5 cases). The reported cases were mainly young and middle-aged males and labour workers before and after the COVID-19 pandemic. The proportion of international students was 15.5% (11/71) before the pandemic, and decreased to 0 after the pandemic (χ² = 5.352, P < 0.05). From 2017 to 2019, the first treatment hospitals and diagnosis hospitals were mainly city-level hospitals, accounting for 62.0% (44/71) and 77.5% (55/71), respectively. From 2020 to 2022, the hospitals for initial treatment and final diagnosis were mainly county-level hospitals, accounting for 15/18 and 12/18, respectively. The proportion of confirmed cases in county-level hospitals was 8.4% (6/71) before the COVID-19 pandemic and increased to 12/18 after the epidemic. The proportion of malaria cases with definitive diagnoses upon admission increased from 42.2% (30/71) before the COVID-19 pandemic to 13/18 after the pandemic (χ² = 26.663, 5.165, all P < 0.05). From 2017 to 2019, the average and median time from the onset of symptoms to the initial treatment for each case were 2.8 d and 2.0 d, respectively. The average and median time from the initial visit to diagnosis were 1.3 d and 1.0 d, respectively. From 2020 to 2022, the average and median time from the onset of symptoms to the initial clinical visit were 1.5 d and 1.0 d, respectively. The average and median time from initial clinical visit to diagnosis were 0.3 d and 0 d, respectively. The interval between the onset of symptoms to initial clinical visit and the time of initial clinical visit to final diagnosis before the pandemic was significantly longer than that after the epidemic (Z = -2.359, -2.658, all P < 0.05). Higher efficiencies for the initial treatment and diagnosis of the malaria cases were observed. The diagnosis of malaria cases in county-level hospitals has been improved after the COVID-19 pandemic in Nanjing City.