Vaccination is a key strategy to prevent the pandemic caused by the coronavirus disease 2019 (COVID-19). This study aims to investigate the willingness of Chinese adults to be vaccinated against COVID-19 and further explore the factors that may affect their willingness. We used a self-design anonymous questionnaire to conduct an online survey via the Sojump. A total of 1009 valid questionnaires were analyzed. The age of the participants ranged from 18 to 74. Among them, 609 (60.4%, 95%CI: 57.4–63.4%) were willing to receive the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. Logistic regression analysis results showed that the age of 30–49 (OR = 2.042, 95%CI: 1.098–3.799), universities and colleges education (OR = 1.873, 95% CI = 1.016–3.451), master degree or above education (OR = 1.885, 95%CI = 1.367–2.599), previous influenza vaccination history (OR = 2.176, 95%CI: 1.474–3.211), trust in the effectiveness of the vaccine (OR = 6.419, 95%CI: 3.717–11.086), and close attention to the latest news of the vaccine (OR = 1.601, 95%CI: 1.046–2.449) were facilitative factors that affected their willingness to be vaccinated. More than half of the adults in China would be willing to receive a SARS-CoV-2 vaccine. Middle-aged people with higher education, those who had been vaccinated against influenza, and those who believed that COVID-19 vaccine was effective and paid close attention to it were more willing to be vaccinated. Our findings can provide reference for the implementation of vaccination and the prevention of COVID-19 in China. More studies are needed after the vaccine is launched.