<p>An electrothermal oil heater includes multiple radiators (3) arranged in turn and side by side and an electric heater. Hollow connecting sleeves (1) which extend horizontally are provided on the upper and the lower ends of the radiators (3), there is an oil guiding groove formed inside the hollow connecting sleeves (1), and the electric heater is located in the oil guiding groove communicated with each other in the hollow connecting sleeves (1). An elongated sheet-shape auxiliary radiator (2) is disposed on the side of one or more radiators (3). The long side of the auxiliary radiator (2) is connected with the side wall of corresponding radiator (3). The auxiliary radiator (2) is located in the space between two adjacent radiators (3).</p>
