Objective To measure the expression level of Myc-interacting zinc finger protein-1 (MIZ1) in peripheral blood mononuclear cells (PBMC) of patients with severe and non-severe community-acquired pneumonia (CAP) and its relationship with inflammatory factors. Methods Thirty-six CAP patients from Beijing Chaoyang Hospital from April 2018 to June 2019 were enrolled in this study. MIZ1 mRNA level in PBMC were measured by reverse transcriptase-quantitative polymerase chain reaction. The levels of interleukin (IL)-6, IL-8, IL-10, and interferon-α in the serum of patients were measured by enzyme-linked immunosorbent assay. The levels of MIZ1 mRNA and inflammatory factors were compared between the severe CAP patients and the non-severe CAP patients. Results Compared with non-severe CAP patients, the MIZ1 mRNA level in the PBMC of severe CAP patients was lower (P<0.05) than non-severe group. Receiver operating characteristic (ROC) curve of the expression level of MIZ1 in PBMC was calculated according to whether CAP was severe or non-severe, and the area under ROC curve was 0.731 (P=0.018). Spearman correlation analysis showed that MIZ1 mRNA was negatively correlated with IL-10 level in the severe CAP patients (Spearman correlation co-efficient was –0.620, P<0.05). Conclusions MIZ1 may indicate the severity of CAP. MIZ1 may affect IL-10 so as to play a role in inflammation regulation.