To reheat crab legs, thaw them and pat them dry with a paper towel. Bring 1 inch of water to a boil in a large pot, and lower the crab legs into the water with a colander.
If necessary, break the crab legs so they fit in the pot. Cover the pot. Cook snow crab legs for five minutes, cook king crab legs for eight minutes or cook Maine or Dungeness crab for 10 minutes. If reheating the crab legs in the oven, preheat the oven to 400 degrees. Thaw and clean the shellfish and wrap it in tented foil. Cook the crab legs in the oven for 20 minutes.