Blood is a product，and the damage caused by unqualified blood belongs to the responsibility of medical products，and the principle of no-fault liability applies. Medical institutions and blood-providing institutions shall apply no-fault liability for external liability，and fault liability for internal recovery. Medical institutions and blood supply institutions need to bear the burden of proof for blood qualification. After blood has been transfused into the human body，blood testing is no longer possible. The judgment of whether the blood is qualified should be combined with the inspection activities of the blood supply institutions and the blood transfusion activities of the medical institutions. In the proof of causality，presumed causality is adopted，and if medical institutions and blood supply institutions cannot prove that there is no causality，they need to bear adverse consequences.