Widening of the ECG p-wave may be caused by intra-atrial block, left atrial hypertrophy, and is commonly seen in diseases such as mitral stenosis, cardiomyopathy, and mitral valve closure insufficiency. P wave is the atrial depolarization wave, and under normal circumstances, the P wave width will not exceed 0.11 seconds. When there is widening of P wave in ECG, it may be caused by intra-atrial block. If it is incomplete intra-atrial block, it is mostly seen in diseases such as mitral stenosis, rheumatic heart disease, cardiomyopathy and so on. If it is complete intra-atrial block, it may be caused by digitalis intoxication, uremia and other diseases. In addition to this, widening of the P wave of ECG may also refer to left atrial hypertrophy, which is usually seen clinically in diseases such as mitral valve insufficiency and mitral stenosis. To sum up, there are many causes of ECG P-wave widening, patients need to do further relevant examinations to clarify the specific causes, cooperate with doctors to carry out standardized treatment, and strengthen the management of daily life, so as to avoid delaying the condition.