Abstract: OBJECTIVE To investigate and analyze the polymorphisms of surface active protein D gene and its influencing factors in patients with type 2 diabetic nephropathy complicated by pulmonary infection. METHODS Totally 90 patients with type 2 diabetic nephropathy admitted to Qianfoshan hospital of Shandong Province from Jan. 2015 to Dec. 2018 were selected. They were divided into 41 cases of infection group and 49 cases of non-infection group according to whether they were complicated by pulmonary infection. The SP-D gene Met11 Thr（rs721917 T/C） polymorphism were detected by PCR-restriction fragment length polymorphism（PCR-RFLP） analysis, and the SP-D levels were detected. Factors influencing pulmonary infection in patients with type 2 diabetes were summarized. RESULTS The SP-D in the serum of lung infection group was（23.74±4.16） ng/L, significantly higher than that of the uninfected group（P＜0.001）. The TT genotype frequency of the rs721917 T/C locus was 14.63%（6/41）, the CT genotype frequency was 31.71%（13/41）, and the CC genotype frequency in the lung infection group was 53.66%（22/41）, significantly different from those of the uninfected group（P＜0.05）. The rs721917 T/C locus C allele frequency 69.51%（57/82） and T allele frequency 30.49%（25/82） in the lung infection group were significantly different from those in uninfected group（P＜0.05）. Age, duration of diabetes, maintenance of hemodialysis, and decompensation of renal function were the influencing factors of pulmonary infection in patients with type 2 diabetic nephropathy（P＜0.05）. CONCLUSION The SP-D level of patients with type 2 diabetic nephropathy complicated by pulmonary infection was increasing, which can provide a reference for the diagnosis of pulmonary infection. The polymorphism of SP-D gene Met11 Thr（rs721917 T/C） might be related to susceptibility to pulmonary infection, the C gene might be a susceptibility gene, and the T genewas a protective gene. In addition, special attention should be paid to susceptible people who were elderly, had a long course of diabetes, required maintenance hemodialysis, and whose kidney function is decompensated, so as to reduce the incidence of lung infection.