Despite the application of various screening methods to patients with hemoptysis, 5% to 15% of patients still have unknown causes of hemoptysis, called occult hemoptysis. Some occult hemoptysis may be due to non-specific ulcers of the trachea and bronchi, varices, early adenomas, small bronchial stones and minor bronchial dilatation. What are the tests for hemoptysis with skin and mucous membrane bleeding? 1.Conventional examination: routine blood and urine examination, examination about coagulation mechanism, antacid bacilli in sputum, tumor cells, lung aspiration of early eggs, common culture of sputum and fungal culture, etc. can help a lot to clarify the etiology of hemoptysis. 2.X-ray examination: Chest X-ray fluoroscopy should be performed for each hemoptysis, and posterior anterior and lateral chest photography, resting layer and CT photography should be performed if necessary. 3.Bronchoscopy: an examination method including electronic bronchoscopy, pediatric bronchoscopy, transbronchoscopic lung biopsy, etc. 4.Electrocardiogram: A technique that uses an electrocardiogram machine to record from the body surface the changes in electrical activity generated by each cardiac cycle of the heart. ECG is the best way to measure and diagnose abnormal heart rhythms. Its the best way to diagnose abnormal heart rhythms when the cardiac conduction tissue is damaged and changes in heart rhythms due to electrolyte imbalance. A detailed examination of the lungs should be performed. When chest x-ray is not yet available, percussion can be used to identify the site of bleeding as early as possible. If hemoptysis begins with diminished breath sounds or (and) rales in one lung and good breath sounds in the contralateral lung field, this often suggests that the bleeding is on that side. Physical examination can also support some specific diagnosis, such as mitral valve diastolic murmur is good for the diagnosis of rheumatic heart disease; the presence of wheezing sounds in the restricted lung and bronchial area often indicates endobronchial lesions, such as lung cancer or foreign body; vascular murmur in the lung field supports arteriovenous malformation; pestle finger is mostly seen in lung cancer, bronchiectasis and lung abscess; enlarged supraclavicular and anterior oblique muscle lymph nodes support metastatic cancer.