Citrus maxima (Burm.) Merr (CMBM) is a traditional digestive tea in China, which is generally considered to have lipid-lowering effect. Here, a bioassay-guided identification of anti-obesity ingredients from CMBM was performed and four compounds were obtained, among which marmin exhibited excellent anti-proliferative activity on 3T3-L1 preadipocytes. Marmin could effectively promote the apoptosis of 3T3-L1 and inhibited its preadipocytes growth through induction of G2/M cell cycle arrest. The ROS levels and apoptotic bodies were increased after marmin treatment on 3T3-L1 preadipocytes, consistent with the results of flow cytometry. Moreover, The RT-PCR analysis revealed that marmin could significantly increase the mRNA expression levels of p53 and the ratio Bax/Bcl-2, but not the p21 mRNA expression. The Western Blotting results showed that marmin could suppress the phosphorylation of p65, extracellular signal- regulated protein kinase 1/2 (ERK1/2) and increase the phosphorylation of c-Jun N-terminal kinase (JNK), which indicated that marmin could induce 3T3-L1 preadipocytes apoptosis by inhibiting nuclear factor kappa-B (NF-κB) and altering mitogen-activated protein kinases (MAPKs) pathway. © 2021 The Authors