Objective To investigate the levels and prognostic value of serum fragment crystallizable gam-ma binding protein(FCGBP)and integrin β4(ITGB4)in elderly patients with severe Mycoplasma pneumoni-ae pneumonia(SMPP).Methods A total of 87 elderly patients with SMPP admitted to Department of Inten-sive Care Medicine in the hospital from January 2020 to December 2023 were selected as the SMPP group,87 elderly patients with general Mycoplasma pneumoniae pneumonia(GMPP)were selected as the GMPP group,and another 87 healthy elderly individuals who underwent physical examinations during the same period were selected as the control group.According to the prognosis after 28 days of treatment,elderly patients with SMPP were divided into a poor prognosis group(31 cases)and a good prognosis group(56 cases).Enzyme linked immunosorbent assay was used to detect serum FCGBP and ITGB4 levels.A multivariate unconditional Logistic regression model was established to determine the factors affecting the poor prognosis of elderly pa-tients with SMPP,and receiver operating characteristic curve was drawn to evaluate the predictive value of se-rum FCGBP and ITGB4 levels for the poor prognosis.Results The serum FCGBP levels in the control group,GMPP group,and SMPP group increased sequentially,while the ITGB4 levels decreased sequentially(P＜0.05).The incidence of poor prognosis in 87 elderly patients with SMPP was 35.63％(31/87).Compared with the good prognosis group,the poor prognosis group showed an increase in serum FCGBP levels and a de-crease in ITGB4 levels(P＜0.05).Age increase(OR=1.200,95％CI:1.036-1.391),high CURB-65 score(OR=2.303,95％CI:1.204-4.403),and high FCGBP level(OR=1.057,95％CI:1.011-1.105)were the independent risk factors for poor prognosis of elderly patients with SMPP(P＜0.05).High oxygenation index(OR=0.980,95％CI:0.963-0.997)and high ITGB4 level(OR=0.961,95％CI:0.929-0.994)were inde-pendent protective factors(P＜0.05).The area under the curve of serum FCGBP combined with ITGB4 level for predicting the poor prognosis was 0.886(95％CI:0.800-0.944),which was larger than 0.789(95％CI:0.689-0.869)and 0.781(95％CI:0.680-0.863)predicted by serum FCGBP and ITGB4 alone(P＜0.05).Conclusion Elevated serum FCGBP levels and decreased ITGB4 levels in elderly patients with SMPP are in-dependently associated with poor prognosis.The combination of serum FCGBP and ITGB4 levels has a high predictive value for poor prognosis in elderly patients with SMPP.