Objective Delirium has been reported in all the course of COVID-19, especially in aged patient with severe SARS-CoV-2 infection, but there are few studies on these millions of patients with none-severe omicron infection. To study the incidence of delirium and its factors in hospitalized elderly patients with non-severe Omicron infection，we reported this single-center observational study. Methods Patients tested positive for SARS-CoV-2 infection at the hospital were included. We used the 3-min diagnostic Confusion Assessment Method for delirium diagnosis. We collected the demographic data, medical history, number of vaccine doses against COVID-19, the first laboratory tests and chest computed tomogram, days to the outcome, and medications to treat COVID-19. Results The data of 311 patients were analyzed, of whom 73 (23.47%) patients were diagnosed with delirium. The five parameters identified as independent factors for delirium were age, body mass index, total protein, albumin-to-globulin ratio, and platelet-large cell ratio. These parameters were used to create a risk prediction model, which showed good predictive accuracy. A decision curve analysis was made, using this model, patients could benefit from the treatment with the incidence from 0.15 to 0.5. Conclusion we found that delirium is frequently seen in elderly patients with non-severe Omicron infection. Age, body mass index, total protein, albumin-to-globulin ratio, and platelet-large cell ratio were identified as independent factors for delirium. These factors are good for delirium, and early detection and preventive action may be taken based on them.