Preoperative preparation for coronary angiography generally includes the following: 1. Complete various tests (including but not limited to routine blood, urinalysis, stool routine + occult blood, liver and kidney function, glucose, lipid analysis, cardiac enzymology such as cardiac enzyme profile, troponin T, pro-brain natriuretic peptide, clotting time, D-dimer, thyroid function, serology, blood electrolytes, electrocardiogram, ambulatory electrocardiogram, cardiac ultrasound, chest X-ray, etc.); 2, Patients should be trained to urinate and defecate in bed several days before the procedure, or be catheterized if they are unable to urinate (this training is not necessary for radial artery interventions today). If coronary angiography is to be performed from the femoral route, preoperative examination of the femoral artery and bilateral dorsalis pedis artery pulsations should be performed. 3. 1 day before the procedure, prepare the skin of both upper limbs and the groin; 4. Routine iodine sensitivity test; 5. 6 to 8 hours before the procedure, fasting (not necessary, but refuse to eat a full meal, seven or eight minutes full is sufficient); 6. For those who are too nervous, give Valium half an hour before surgery. 8.Tell the patient to urinate and remove the body ornaments and avoid nail polish before surgery. 9.Continue to standardize the medication, do not stop using. 10.Diabetic patients should generally discontinue metformin for more than 48 hours before surgery, because metformin may aggravate the renal damage of the contrast agent.