A heater and a heating method for a wet extraction tank, said heater comprising a heating tube comprising a spiral glass tube with an air inlet and an air outlet; the air inlet is connected to a steam supply apparatus via a steam tube, and the air outlet is in communication with an apparatus containing micro-steam or hot water; the steam tube has with a pressure regulating valve for adjusting the steam pressure inside the heating tube; the glass tube is fixedly connected to the extraction tank by a wooden material fixed to the tank via a stainless steel bolt; the glass tube is fixed to the wooden material by wrapping and welding a heat and chemical resistant soft plastic sheeting. The heating method comprises maintaining the liquid inside the tank in a constant state of ebullition so that heat is evenly and uniformly distributed throughout the tank.