Introduction: Accumulated evidences have shown the role of physical exercise in patients with nonalcoholic fatty liver disease (NAFLD), but the conclusions were not consistent. Objectives: The aim of this study was to investigate the accurate effect of physical exercise and the optimal mode of physical exercise on liver enzymes and body mass index (BMI) in adults NAFLD patients. Methods: PubMed, Embase database and Cochrane Library databases were searched for the relevant trials which were published up to August 2019. The analysis was restricted to the studies which examined the effect of supervised exercise intervention on liver enzymes (Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST)) and BMI. Fifteen randomized controlled trials (893 adults) were eligible for inclusion in this meta-analysis. Results: The aerobic exercise could reduce the ALT levels markedly compared to the resistance exercise and the combined aerobic and resistance exercise. The combined aerobic and resistance exercise could reduce the AST levels significantly. The aerobic exercise could reduce the BMI markedly other than the resistance exercise and the combined aerobic and resistance exercise. The exercise duration times>12 weeks and frequency>3 times per week were tightly associated with the decreased ALT, AST and BMI. Conclusion: physical exercise could reduce the serum levels of ALT, AST, and BMI in adult NAFLD patients effectively. Aerobic exercise more than 3 times per week and duration of more than 12 weeks may be the optimal mode of exercise for the improvement of NAFLD in adults.