<p>The International Prognostic Index (IPI) and IPI related prognostic indexes are widely used for risk-stratification in lymphoma. However, identifying poor prognostic group patients remains a significant objective. This study aimed to develop a predictive prognostic model for DLBCL treated with R-CHOP immunochemotherapy. A cohort comprising 167 individuals newly diagnosed with DLBCL between January 2016 and June 2021 at Jiangsu cancer hospital, Nanjing Medical University were enrolled for investigation. Univariate and multivariate Cox analysis were used for variable selection. The Akaike information criterion (AIC) guided the selection of factors for constructing the nomograms, along with a novel prognostic index for assessing both progression-free survival (PFS) and overall survival (OS). Internal validation was performed with the bootstrap method(B = 1000). Age, Lactate dehydrogenase (LDH), stage, extra-nodal sites and absolute CD4 + T cell counts (ACD4C) were associated with both PFS and OS. These discerned prognostic factors were subsequently employed in constructing nomograms for PFS and OS, respectively. The C-indexes of Internal validation performed with the Bootstrap method were 0.76 (PFS: 95%CI 0.67–0.80),0.81(OS:95%CI 0.72–0.85), respectively. The calibration plots, alongside internal bootstrap resampling, demonstrated commendable consistency between predictions and observations. For enhanced clinical applicability, we devised a novel immune prognostic index, categorizing DLBCL patients into four distinct risk groups: low, low-intermediate, high-intermediate, and high risk, corresponding to 0, 1–2, 3, 4–5 risk factors respectively. Kaplan-Meier analysis underscored the superior discriminatory capacity of the immune index in assessing the prognosis across various risk groups. The proposed immune index is a useful tool to predict the prognosis of DLBCL patients treated with R-CHOP immunochemotherapy in this study.</p>