OBJECTIVE: To systematically review the risks and benefits of metformin in treatment of non-alcoholic fatty liver disease（ NAFLD） complicated with type 2 diabetes

so as to provide evidence-based evidence for the effectiveness and safety of metformin in treatment of NAFLD complicated with type 2 diabetes. METHODS: Cochrane systematic review was adopted to retrieve and screen the randomized controlled trials [the intervening measure of metformin group was given metformin for treatment

with or without lifestyle intervention; the intervening measure of control intervention group was given placebo or blank control（ untreated group） or other drugs（ other drug group）

with or without lifestyle intervention; the administration route

dosage and treatment course were not limited]for metformin in treatment of NAFLD complicated with type 2 diabetes. Rev Man 5. 2 was adopted to conduct Meta analysis after data extraction and methodological quality evaluation. RESULTS: A total of 15 studies were involved

including 1 306 patients; the quality of involved studies was uneven

the long-term overall mortality rate

the need for liver transplantation and the incidence of hepatocellular carcinoma after drug intervention were not studied and reported. Results of Meta analysis indicated the BMI of metformin group was significantly lower than that of the untreated group

with statistically significant difference（ MD =-2. 07

95% CI =-2. 54--1. 60

P < 0. 001）; as for the safety

the incidence of adverse drug reactions of metformin group was significantly higher than that of the untreated group（ OR = 14. 09

95%CI =3. 27-60. 72

P<0. 001） and other drug group（ OR = 3. 64

95%CI = 1. 54-8. 61

P<0. 001）

with statistically significant differences. However

no severe adverse drug reactions occurred during the treatment

and most of adverse drug reactions were tolerable for patients. CONCLUSIONS: It remains uncertain whether metformin can delay the progression of NAFLD complicated with type 2 diabetes

while its effect in reducing body mass index may be beneficial to patients.