Objective: To investigate the correlation and causal relationship between blood uric acid and abnormal liver function in metabolic associated fatty liver disease (MAFLD). Methods: 114 patients with MAFLD were included in West China Hospital of Sichuan University. Spearman correlation and multivariate logistic regression were used to analyze the correlation between uric acid, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). The causal relationship between uric acid and liver function was analyzed by Mendelian randomization. Results: Blood uric acid was positive correlated with ALT and AST, with correlation coefficients of 0.51 (P<0.001) and 0.42 (P=0.01), respectively. Higher uric acid levels significantly increased ALT and AST levels (OR: 7.39, P=0.01; OR: 3.84, P=0.05). For each 1 standard deviation (SD) increased in genetically predicted uric acid, ALT increased by 0.07 SD (P=0.002) and AST by 0.06 SD (P=0.03). However, no statistical difference has been found between ALT, AST and uric acid in reverse causation. Conclusion: Blood uric acid could cause elevated ALT and AST levels, and might be a potential risk factor for impaired liver function in patients with MAFLD.