Bruising after venous blood collection is a manifestation of blood leaking out of the blood vessels and seeping into the subcutaneous tissue. The main reason for this is that during venous blood collection, due to the relatively thick needle, the puncture hole is not pressed exactly or not pressed long enough after the blood is collected, resulting in blood leaking out of the blood vessel along the puncture hole and freeing into the subcutaneous tissue, which appears as bruising from the skin surface. When bruising after venous blood collection occurs, it is necessary to clarify whether there is continued local enlargement of the hematoma, which can be clarified by ultrasonography. If there is continued extravasation of blood, local pressure bandage with elastic bandage is recommended; if there is no continued increase of hematoma, local cold compress is recommended to promote local bruise absorption or to take continued compression to improve the symptoms.