15-20 minutes. Steaming butter crabs in an ordinary steamer usually takes 15-20 minutes, and steaming with a pressure cooker takes even less time. Do not steam dead butter crabs, which accumulate toxic substances in their bodies. When steaming butter crabs, first knock the butter crab stunned or frozen numb, to prevent the butter crab to break free from the broken, incomplete butter crab steaming will leak oil affect the taste.