Objective To explore the dynamic changes of serum potassium (K) level in patients with chronic heart failure (CHF) and its predictive value for major adverse cardiovascular events (MACE). Methods A retrospective analysis was performed on 122 patients with CHF who were acutely aggravated and treated in our hospital from May 2022 to April 2024. According to whether or not they had MACE occurrence, the patients were divided into MACE occurrence group (n=76) and MACE non-occurrence group (n=46). The clinical data between different groups with patients was analyzed by t test and χ2 test. The Cox regression was used to analyze the relationship between K level and the risk of MACE in CHF patients. The receiver Operating characteristic (ROC) curves assess the sensitivity, specificity, and accuracy of the variables. The restrictive cubic spline (RCS) model was used to analyze the dose-response relationship between K level and the risk of MACE in CHF. The Log-binomial regression model was used to analyze the correlation between K level and the occurrence of MACE and its subtypes. The multiple linear regression analysis was used to test the correlation between K level and oxidative stress under different cardiac functions. The multiplicative interaction model and additive interaction model were used to analyze the K level and oxidative stress related indexes on MACE in CHF patients. Results The diabetes, cardiac function grade, total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), glycated hemoglobin (HbA1c), N-terminal probrain natriuretic peptide (NT-proBNP), K, oxidative stress index (OSI), left ventricular ejection fraction (LVEF), and left ventricle end-systolic diameter (LVEDD), left ventricular end-diastolic diameter (LVESD), frontal QRS-T Angle and QRS duration in the MACE group and the non-MACE group were significant differences (P＜0.05). At 1, 3, 7 and 14 days after treatment, the difference of K level was statistically significant (P＜0.05). The K level of patients with different cardiac functions was significantly different before treatment and at 1, 3, 7 and 14 days after treatment (P＜0.05). The risk of MACE in CHF patients decreased with the increase of K level, and after adjusting for covariates, there was still statistical significance between K level and MACE risk in CHF patients (P＜0.001). The K diagnosis effect was better (AUC=0.804＞0.7, P＜0.05), sensitivity, specificity and accuracy were high. The risk of MACE decreased with the increase of K level in a nonlinear dose-response relationship (P for non linear＜0.05). The result of Log-binomial regression model showed that K level was negatively correlated with the occurrence of MACE and its subtypes (RR＜1). The result of multiple linear regression showed that K level was negatively correlated with OSI and MDA. A low level of K had additive and multiplicative interactions with a high level of TOS, a high level of MDA, and a low level of SOD. In patients with CHF, those with low K level, low SOD level, concurrent with high TOS level and high MDA level, had a significantly higher risk of MACE. Conclusion The dynamic changes of K level in CHF patients are closely related to the the risk of MACE. The K level is an independent predictor of MACE. With the K level decreases, and the risk of MACE increases significantly. The K level can effectively predict the risk of MACE in CHF patients, which has high diagnostic efficiency and clinical practical value