Objective:To investigate the role and mechanism of celastrol in the treatment of relapsed/refractory diffuse large B-cell lymphoma(DLBCL)by inducing ferroptosis.Methods:The rituximab-resistant lymphoma cell line SU-DHL-2-R was established by the concentration gradient method. The CCK-8 assay was used to determine cell viability after treatment with different concentrations of celastrol. SU-DHL-2-R cells were divided into control group, celastrol group, ferroptosis inhibitor(Fer-1)group, and celastrol+Fer-1 group. qRT-PCR and Western blotting were used to detect the expression levels of ferroptosis-related genes SLC7A11 and GPX4. GSH and Fe²⁺levels were detected using commercial kits, and reactive oxygen species(ROS)levels were detected using the DCFH-DA probe method. The protein expressions of PI3K, p-PI3K, Akt and p-Akt were detected by Western blotting. SU-DHL-2-R cells were injected subcutaneously into SCID mice to establish lymphoma tumor bearing mouse models. The tumor bearing mice were divided into control and celastrol treatment groups. The survival status of the mice was monitored and tumor volume was measured. The expressions of SLC7A11 and GPX4 in the lymphoma tissues of the mice were detected by immunohistochemistry.Results:The SU-DHL-2-R cell model was successfully established, and the drug resistance index was 12. Celastrol significantly inhibited the proliferation of SU-DHL-2 and SU-DHL-2-R cells. Compared with the control group, the mRNA and protein expressions of SLC7A11 and GPX4 were downregulated, the level of GSH was decreased, ROS accumulation was induced, Fe²⁺levels was increased, and the protein expression levels of p-PI3K and p-Akt were significantly downregulated in the celastrol group. However compared with the celastrol group, the above changes were attenuated in the celastrol+Fer-1 group. The tumor-bearing mouse model of lymphoma was established. Compared with the control group, the tumor volume of mice treated with celastrol was reduced, and the expression of SLC7A11 and GPX4 was significantly decreased.Conclusion:Celastrol may inhibit the progression of relapsed/refractory DLBCL by inducing ferroptosis through targeting the PI3K/Akt pathway.