The black color of the sputum coughed up is mainly considered to be caused by the pollution of the work and living environment and the frequent inhalation of black dust, which will stimulate the respiratory tract to produce increased secretions. Black dust together with these secretions through coughing out of the body to form black sputum. Frequent smoking also has a great impact, the tar in tobacco will be deposited in the trachea and lungs, which will also stimulate the respiratory tract to cause chronic inflammation, and will cough up black sputum. When you have a respiratory infection, you will also cough up black sputum and it will be sticky, so you need to go to the respiratory medicine department for examination, and you need to take blood tests for routine blood tests, and you also need to take a chest X-ray and do sputum examination. If you have a respiratory tract infection, you can use effective antibacterial medication, pay attention to protection at work, and quit smoking in time.