Objective To analyze the relationship between the occurrence of hypokalemia and the incidence of malignant arrhythmia in patients with early myocardial infarction. Methods 417 cases of myocardial infarction patients in our hospital from Jan.2013 to Jan.2017 were collected as the research objects. The clinical data of these patients were retrospectively analyzed, the relationship between the occurrence of hypokalemia and the incidence of malignant arrhythmia was statistically investigated, and the changes of serum potassium level and electrocardiogram in patients with hypokalemia induced malignant arrhythmia were compared. Results The incidence rate of hypokalemia in these 417 myocardial infarction patients was 20.14%, and the inter group analysis showed that there was no significant difference in general information as age, sex, hypertension and drug use between the patients with hypokalemia and patients with normal serum potassium (P>0.05), at the same time, the incidence rate of malignant arrhythmia in patients with hypokalemia was 39.28% (28 cases with premature ventricular contraction, 3 cases with sustained ventricular tachycardia, 1 case with short terminal ventricular tachycardia and 1 case with ventricular fibrillation) which was significantly higher than that in patients with normal serum potassium 18.91%; after treatment, the serum potassium levels in patients with hypokalemia were returned to normal range, the incidence of malignant arrhythmia was also reduced to 8 (24.24%) cases, and the inter and intra-group differences of above indicators were statistically significant (P<0.05). Conclusion The risk of hypokalemia in patients with early myocardial infarction is greater, while the risk of malignant arrhythmias in patients with hypokalemia is higher than that in patients with normal serum potassium, therefore, attention should be paid to the occurrence of hypokalemia, and positive prevention and treatment should be given in clinic.