The purpose of this study is to construct a mouse model of pulmonary infection by multidrug-resistant Acinetobacter baumannii (A. baumannii), and to evaluate the changes in various inflammatory indicators in the model mice, so as to provide a reference for studying the pathogenicity of multidrug-resistant A. baumannii in vivo. First of all, polymerase chain reaction (PCR) was used to detect the distribution characteristics of virulence genes of A. baumannii. And then, Caenorhabditis elegans was infected with different A. baumannii strains for screening the strain used in modeling. The results demonstrated that strain A5 not only carried more virulence genes, but also had stronger pathogenicity. Immunosuppression was induced by injection of cyclophosphamide in mice. Selected strain A5 solution (high and low density) was inhaled by nebulization in immunosuppressive mice. The health state, lung tissue changes, colony counts in lung tissues and bronchoalveolar lavage fluid (BALF), peripheral blood leukocyte and neutrophil counts, and cytokine changes in mice were monitored. Compared with the control group, the mice infected with strain A5 showed significantly worse state, pulmonary hyperemia and edema. Meanwhile, A. baumannii showed proliferation in the lungs and BALF of mice. The number of peripheral leukocytes and neutrophils in the high density group increased more obviously than that in the low density group (Leukocyte: F＝78.630, P＝0.000; Neutrophil: F＝4.762, P＝0.053). Compared with the control group, the level of interleukin 6 (IL-6) in the mice infected with A5 strain was higher and tended to be stable (F＝14.382, P＝0.001), but the level of tumor necrosis factor α (TNF-α) kept increasing (F＝4.558, P＝0.032). Moreover, the variation trend of TNF-α between high and low density groups was not completely consistent. In this study, a mouse model of pulmonary multidrug-resistant A. baumannii infection is successfully constructed. The model mice shows obvious symptoms of infection, and A. baumannii load is positively correlated with the degree of infection in the mice.