〔Abstract〕 Objective To analyse the level of vitamin D in patients with coronavirus disease 2019 (COVID-19) in Shenzhen Third People's Hospital. The hospital is the designated medical institution for patients with COVID-19 in Shenzhen. Methods Serum level of 25-hydroxyvitamin D [25(OH)D] was measured in patients with COVID-19 from 13 December 2021 to 25 February 2022. The patients were admitted to Shenzhen Third People's Hospital with COVID-19. Their level of 25(OH)D was compared between different age and gender groups, and with those of the population who underwent a physical examination in Guangdong province. Results There was no statistically significant difference in the level of 25(OH)D between men and women of COVID-19 in Shenzhen (P > 0.05). The level of 25(OH)D in the age group < 30 years was the lowest, and the level of 25(OH)D in the age group 40-49 years was the highest. There was a statistically significant difference between the groups (P < 0.05). The average serum level of 25(OH)D patients with COVID-19 in Shenzhen was (54.13 ± 14.80) nmol·L^-1, which was lower than that of people with physical examination in Guangdong, with a statistically significant difference (P < 0.05). And the vitamin D adequacy rate of COVID-19 people (8.7%) was lower than that of the people who were examined (25.9%), with a statistically significant difference (P < 0.05). Conclusion The level of vitamin D in people with COVID-19 in Shenzhen were generally low, and lower than the level of the physical examination population in Guangdong, with a large number of deficiencies and insufficiencies, especially in the < 30 years old age group. There is a possibility that the level of vitamin may be correlated with the incidence of COVID-19. Considering that vitamin D has multiple correlations with health, appropriately increasing the level of vitamin D maybe have a positive effect on health.