Objective To explore the changes of RDW and cTnI in the serum of patients with severe pneumonia and their diagnostic value for myocardial injury. Methods  Selected 80 patients with severe pneumonia diagnosed in Wujin People’s Hospital from January 2014 to December 2019. According to whether they were finally diagnosed with myocardial damage, they were divided into 29 cases in group A (with myocardial damage) and 51 cases in group B (without myocardium). Injury), 60 patients with common pneumonia during the same period were selected as the control group; the peripheral blood RDW and serum cTnI levels of the three groups were compared. Results  The RDW and cTnI test results of group A patients were significantly higher than those of group B and control group, and the difference was statistically significant (P<0.05); There was no statistically significant difference in RDW and cTnI between group B and the control group (P>0.05); Using ROC curve analysis, the results showed that the sensitivity of RDW in diagnosing severe pneumonia patients with myocardial damage was 88.51%, the specificity was 76.29%, and the AUC value was 0.846; the sensitivity of cTnI in diagnosing severe pneumonia patients with myocardial damage was 94.20% and the specificity was 86.44 %, the AUC value is 0.903; The sensitivity of cTnI combined with RDW in diagnosing severe pneumonia patients with myocardial damage was 98.28%, specificity was 92.01%, and the AUC value was 0.951. Conclusion. Patients with severe pneumonia may be complicated with myocardial injury. The combination of cTnI and RDW examination has certain guiding value for early diagnosis and has guiding significance for clinical treatment.