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An experimental device of ventilation system was established to meet the requirement of freshkeeping transportation with controlled atmosphere by liquid nitrogen. The pressure drop characteristics of the ventilation system were studied. The effects of airflow velocity, ratio of open area, stack mode and length of return air channel on the characteristics of pressure drop and energy consumption were analyzed. The pressure drop characteristics could be described by the equation of Ramsin. The pressure drop increased with the addition of airflow velocity. At the same airflow velocity, the pressure drop decreased with the addition of ratio of open area. The distribution of pressure drop in freshkeeping room was steady. The effect of three stack modes on the pressure drop was not striking. The pressure drop was less when there was no return air channel. When the ratio of open area of the separator with holes in freshkeeping transportation vehicle was bigger than 3.89%, it could meet low pressure loss and had small energy consumption. The research achievements will be instructive to the design of the ventilation system in freshkeeping transportation with controlled atmosphere. 