Objective: To investigate the correlation analysis between tumor related indicators of diffuse large B-cell lymphoma (DLBCL) and lactate dehydrogenase (LDH) and prognosis in ¹⁸F-FDG PET/CT imaging before treatment. Methods: A total of 78 patients with pathologically confirmed DLBCL were selected and ¹⁸F-FDG PET/CT imaging performed before treatment. We analyzed the correlation of tumor related markers [maximum standard uptake value (SUV_max), metabolic tumor volume (MTV), total glycolysis of lesions (TLG)] with the level of LDH and prognosis related factors [Ann Arbor stage, international prognostic index (IPI), number of involved nodular sites] by Spearman correlation analysis. With progression-free survival (PFS) as the positive event, the optimal cut-off values of SUV_max, MTV and TLG were obtained through the receiver operating characteristic (ROC) curve. Three-year PFS rates were statistically analyzed, and Cox proportional hazard model was used to analyze independent factors affecting the PFS rate. Results: There was no correlation between SUV_max and Ann Arbor stage, IPI score and the number of involved nodular sites (P>0.05). MTV and TLG were positively correlated with the LDH level, Ann Arbor stage and IPI score (all P<0.05). At the end of follow-up, the median PFS time of 78 patients was 33 months, and the 9-year PFS rate was 46.15%. The cut-off values of SUV_max, MTV and TLG were 20.20, 55.86 cm³ and 816.69 g respectively, with PFS as the positive event. Cox multivariate regression analysis showed that Ann Arbor stage, IPI score, MTV and TLG were independent influencing factors of PFS rate in patients with DLBCL. Conclusion: MTV and TLG in ¹⁸F-FDG PET/CT imaging before treatment are positively correlated with LDH. Ann Arbor stage and IPI score which are independent factors influencing the PFS of patients with DLBC, while SUV_max is of little significance for predicting the prognosis.