W type electric heating tube, U type electric heating tube is filled with heating wire in seamless metal tube (carbon steel tube, titanium tube, stainless steel tube, copper tube), and the gap portion is filled with magnesium oxide powder with good thermal conductivity and insulation. The shrink tube is formed and then processed into various shapes required by the user. The utility model has the advantages of simple structure, high thermal efficiency, good mechanical strength and good adaptability to harsh environments. It can be used for heating various liquids and acid-base salts, as well as for metal melting and melting at low melting point (lead, zinc, tin, babbitt). Users can provide drawings for special design and processing.