Battery preheating at low temperatures is essential to ensure the efficient operation of electric vehicles in all climate conditions. Alternating current heating is proposed as an effective preheating method to improve the poor performance of lithium-ion batteries operated at low temperatures. To describe the dynamic voltage behavior accurately, the Butler-Volmer equation has been employed, and then a novel electro-thermal coupled model has been proposed for accurately calculating the thermal behavior of a battery. To obtain the optimal preheating performance, the electro-thermal coupled model-based available heating current computational method has been developed to obtain the optimal echelon preheating strategy. This method has the potential to balance the heat generation rate and degradation on battery lifetime. Finally, the proposed echelon heating strategy has been verified by battery cells and battery packs. Results show that the battery cell can be heated from the temperature of −20.3 °C to 10.02 °C by 13.7 min with an average temperature-rise 2.21 °C/min. And the battery pack can be heated from −20.84 °C to 10 °C by 12.4 min with an average temperature-rise is 2.47 °C/min.