Abstract: Abstract: The forced air cooling was widely used as the cooling method of battery pack with natural wind or air-conditioning wind, the research mainly focused on how to balance the flow condition of every modes of battery pack. Because the forced air cooling had the characteristics of simple structure, low cost and high maintainability, so it could better meet the operating requirements of modern electric farm-oriented vehicle. Different inlet modes of battery pack would affect the heat dissipation performance of forced air cooling, through the simulation calculation method to study it's effects on the heat dissipation performance of different inlet modes; it would generate great significance for choosing inlet mode and structure optimization design. Combination with thermal power of 55 Ah lithium-ion battery monomer at different charge and discharge rates, the paper selected the horizontal battery pack with forced air cooling as study object, and researched on the influence of inlet mode to the heat dissipation performance at different conditions (including sustained acceleration, sustained deceleration, pause and pulse discharge processing, electric vehicle practical work) with FLOEFD software, the results showed that: the temperature rising of horizontal battery pack was significantly higher than temperature difference based on different conditions, in the case of longitudinal inlet mode, the maximum temperature rising and temperature difference of battery pack at the end time of sustained acceleration were 3.91℃ and 2.24℃; the maximum temperature rising and temperature difference of battery pack at the end time of sustained deceleration were 4.91℃ and 3.70℃; the maximum temperature rising and temperature difference of battery pack at the end time of pause and pulse discharge processing were 5.17℃ and 2.94℃; the maximum temperature rising and temperature difference of battery pack at the end time of electric vehicle practical work were 7.36℃ and 5.40℃.The maximum temperature rising and temperature difference of longitudinal inlet mode were lower than horizontal inlet mode, among them, the maximum temperature rising and temperature difference at the end time of sustained acceleration of longitudinal inlet mode were lower by 0.01℃ and 0.03℃ than horizontal inlet mode; the maximum temperature rising and temperature difference at the end time of sustained deceleration of longitudinal inlet mode were lower by 0.14℃ and 0.03℃ than horizontal inlet mode; the maximum temperature rising and temperature difference at the end time of pause and pulse discharge processing of longitudinal inlet mode were lower by 0.03℃ and 0.01℃ than horizontal inlet mode; the maximum temperature rising and temperature difference at the end time of electric vehicle practical work of longitudinal inlet mode were lower by 0.36℃ and 0.08℃ than horizontal inlet mode. The longitudinal inlet mode would improve the heat dissipation performance of battery pack with forced air cooling. The reference basis for choosing inlet mode and structure optimization design of electric farm-oriented vehicle with battery pack would be offered.