Mental health is a major public health issue that affects social development. This study aims to explore the psychological state of residents of Hainan Island and its influencing factors during the COVID-19 pandemic and to provide a scientific basis for the formulation of psychological counseling measures to be used after the pandemic. We used the nonprobability snowball sampling method to conduct an online survey from February 21 to February 28, 2020, and collected a sample of 533 respondents. Using a binary logistic regression model and network analysis, the psychological state of residents and the main factors were analyzed during the concentrated outbreak of COVID-19 (from January 20 to February 16, 2020). The study found that during the pandemic, 92.7% of the respondents were in a poor state of mind, and 54.2% experienced severe psychological stress. The mental state is spatially expressed as a pattern of "high in the middle and low in the surroundings." Second, within the four-week sample, the overall psychological tension showed an inverted U-shaped trend. Respondents feeling stressed were most common in the second week, when they accounted for 87.99% of the total. Third, individual characteristics such as gender, age, fixed expenditure, and family size significantly affect the mental state. Women, the elderly, residents with fixed expenditures, and residents with large families are at greater risk of psychological stress. Finally, external factors such as the distance between residents and the location of cases and the node degree of the pandemic transmission network have a significant impact on the psychological state. However, residents in the least developed areas of Hainan Island, which are far away from active cases and have a low node degree, are more prone to psychological pressure. The government needs to pay special attention to these groups when constructing a long-term mechanism of psychological crisis intervention and increase public health resource investment in underdeveloped areas.