The patient’s pleural fluid can usually be roughly quantified under ultrasound and categorized into small, moderate and large amounts. Normally pleural effusion below 300mL is a small amount of pleural fluid, while if it is 300-500ml, it is a moderate amount, and if it is more than 500ml, it is called a large amount of pleural fluid. Ultrasound can only make a general judgment, and the size of the patient also needs to be taken into account.Ultrasound is not very accurate in quantifying pleural effusion, but under ultrasound guidance, pleural fluid puncture tube placement is the most convenient.