Objectives To study the effect of ketogenic diet （KD） on liver lipid deposition in db/db mice, and to investigate the safety of KD treatment and molecular mechanism in db/db mice. Methods Twenty eight-week-old db/db male mice of obesity type 2 diabetes mellitus(T2DM) were selected. After 3 weeks of adaptive feeding, 18 mice were enrolled and randomly divided into 3 groups: normal feeding (ND) group (n=6), KD group (n=6) and 75% caloric restriction (CR) group(n=6). In addition, 6 eight-week-old C57BL/6 male mice were fed with standard control diet and considered as normal (C) group. C and ND groups were free to get the standard feed, KD group was free to get the ketogenic feed, and CR group was the positive control group, which consumed 75% of standard feed calories of ND group each day. After 4 weeks of diet treatment, 2 mice in KD group and 1 mouse in CR group died. Three mice in each group were randomly included for statistical analysis, and the levels of fasting triglyceride(TG), total cholesterol(TC) and low-density lipoprotein cholesterol(LDL-C) in each group were detected and compared. The morphology and structure of liver were observed by hematoxylin and eosin(HE) staining. The size and number of lipid droplets in liver tissue of mice were observed by oil red O staining. The quantitative polymerase chain reaction (qPCR) was used to detect the expression of sterol regulatory element-binding protein 1C (SREBP1C), stearoyl-CoA desaturase 1 (SCD1), acyl-CoA oxidase 1 (ACOX1), peroxisome proliferator-activated receptor α (PPARα), cluster of differentiation 36 (CD36), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), matrix metalloproteinase-13 (MMP13), matrix metalloproteinase-inhibitor 1(TIMP1), collagen type Ⅲ alpha 1 (COL3a1) and collagen type Ⅰ alpha 1 (COL1a1) in liver. Immunohistochemistry (IHC) and western blot (WB) were used to detect the expression of fatty acid translocase (CD36) in liver tissues. Results After 4 weeks of dietary intervention, compared with ND group, the level of TG, TC and LDL-C in KD group was not improved, but the level of TG in CR group was significantly decreased (P<0.05). HE and oil red O staining showed that liver vacuolar degeneration and lipid deposition increased in KD group compared with ND and CR groups. qPCR showed that compared with ND group, lipid-catabolism genes such as PPARα and ACOX1 showed decreased trend in KD group without significant difference; the expression of CD36, IL-1β and TNF-α was significantly increased (P<0.05). The expression of MMP13 was significantly decreased(P<0.05), while the expression of other hepatic fibrosis related genes was not changed. IHC showed that compared with ND group, the expression level of CD36 protein in KD group was significantly increased(P<0.05). Conclusions KD could induce liver lipid deposition, aggravate liver inflammation in db/db mice. Therefore, in the treatment of obesity with KD, the changes of liver function should be closely observed to prevent the occurrence of adverse reactions.