Abstract: Objective To explore the relationship between blood potassium variability，acute kidney injury（AKI）and in-hospital mortality in patients with acute myocardial infarction（AMI）. Methods Basic profiles and blood potassium were retrospectively reviewed for 7210 AMI inpatients at Department of Cardiology in 8 hospitals. Range of changes，standard deviation，coefficient of variation，maximal fluctuation rate，maximal value of fluctuation per detection day and average value of fluctuation per detection day were measured as parameters of blood potassium variability. Furthermore，subgroup analyses were performed according to whether or not diuretics or renin-angiotensin system blockers were used. Results Among them，810（11. 2%）had concurrent AKI. Compared with those without AKI，no significant difference existed in potassium levels in AKI patients. However，variability of potassium was higher. Multivariable adjusted Logistic model revealed that higher serum potassium variability was an independent risk factor for in-hospital mortality；as compared with non-AKI and variation ≥0. 4 mmol/L per testing day［OR 2. 06，95% confidence interval（1. 07-3. 98）］，AMI patients with AKI and variation ≥0. 4 mmol/L per testing day had a significantly higher risk of mortality［OR 30. 82，95% confidence interval（16. 73-56. 78）］. Conclusion AKI is associated with potassium variability in AMI patients. Blood potassium variability is independently associated with in-hospital mortality. The risk of inhospital mortality further spikes when AKI is coupled with higher potassium variability. The changes in blood potassium in AMI patients with AKI should be closely monitored clinically.