The invention discloses an automatic heating and heat preservation device of electric car range extender diesel engine oil conveying pipes. The device comprises a tee joint, an electric heating pipe,a first oil conveying pipe, a second oil conveying pipe, an oil collection box, a gas conveying pipe, a three-position three-way electromagnetic reversing valve, a temperature sensor, an exhaust fan and a control panel; the control panel is an ECU intelligent circuit control system, the oil tank is connected with the first oil conveying pipe and the second oil conveying pipe through two oil outlets of the tee joint via the oil pump, the oil conveying pipes are connected with two oil inlets of the three-position three-way electromagnetic reversing valve, the control panel is connected with theelectric heating pipe, the electromagnetic valve, the three-position three-way electromagnetic reversing valve and the exhaust fan through a wire and a data signal line, the control panel controls a diesel engine to generate electricity according to the SOC of a power battery, the electric heating pipe is controlled to heat the first oil conveying pipe, the exhaust fan is controlled to carry out hot air exhaust work according to the reverse hysteresis output characteristic schmitt trigger control principle, fuel in the oil collection box and the second oil conveying pipe is heated, flowing andcombustion of diesel oil are improved, the fuel oil conversion efficiency is improved, energy is saved, and the fuel oil cost is reduced.