In valve surgery cases among Mongolia, post-arrhythmia is observed that as same as pre-arrhythmia by its kind and prevalence. Which is why post-operation complication, mortality, financial problems are high, also exceeding hospital care. Therefore we aimed to compare pre and post operation arrhythmia in patients who had aortic and mitral valve surgery. In order to compare, we measured pre and post surgery electrocardiogram from total 30 patients with satisfaction. Statistical analyses are completed by SPSS 23 software and the p-value is evaluated as significant when less than 0.05. The average age of patients were 43./±3/. The frequency of pre-surgery arrhythmia were 88.7% hence atrial fibrillation were 62.9%, moreover post-surgery arrhythmia were 80%. There was no statistically significant difference between pre and post surgery arrhythmia (p= 0.9). According to the result, we have concluded that arrhythmia frequency hasn’t been getting lower after valve surgery, consequently needed to improve arrhythmia control, treatment and admit novel methods such as Cox maze IV, and Catheter ablation.