Bone marrow extraction is done by bone marrow aspiration. Before doing bone marrow aspiration, firstly, we should explain to the patient the significance of doing bone marrow aspiration to dispel the patient’s nervousness, generally take the patient’s posterior superior iliac spine as the puncture point, routinely disinfect the skin, wear sterile gloves, lay sterile cavity towel, then extract 2% lidocaine 2ml with a 5ml syringe, infiltrate from the skin to the periosteum layer by layer, after local anesthesia, hold the puncture needle through the skin to the periosteum, penetrate layer by layer, after reaching the periosteum After reaching the periosteum, the needle should be rotated from side to side so that the bone marrow puncture needle gradually enters the bone marrow cavity, and then the bone marrow fluid is extracted with a dry syringe for relevant examination. After the bone marrow fluid is extracted, the needle is removed, the puncture site is disinfected, covered with gauze, and the patient is told to keep the puncture site dry for 48 hours, and the whole procedure is completed.