The purpose of this research was study different the clinical, subclinical characteristics and risk factors in patients with Wolff - Parkinson - White (WPW) syndrome between those with and without atrial fibrillation underwent electrophysiological study. Subjects and Methods: A total of 49 patients with WPW syndrome in the Vietnam Heart Institute at Bachmai Hospital (period august, 2020 to august, 2021) were divided into two groups: Those with AF (group 1, n = 18) and those without AF (group 2, n = 31). We compared the clinical, subclinical and risk factors between two group of patients with and without AF attacks. Results: The results showed that the average age of 43,8 ± 17,6 years. There was a different in the percentage of the man in the WPW group with AF higher than the WPW without AF (83,3% vs 48,3%), p < 0,05; the percentage of the women in the WPW group with AF lower than the WPW group withour AF (38,8% vs 51,7%), p < 0,05. Patients has symptoms of lightheadedness and fainting in the group with AF (27,8%) higher than the group without AF (6,6%) with statistical significance (p < 0,05). On the Electrocardiogram of the WPW patients in AF attack has average heart beat is 205 ± 47 beats/minute and the shortest RR is 246 ± 40 ms. There was no significant different in the wpw between the two groups about the subclinical (hematology, biochemical and electrocardiogam) and risk factors.