Abstract: Granary with ventilation troughs, as widely used in China, is a kind of granaries with rectangular flat base ventilation troughs built on the ground, and positive pressure ventilation is generally adopted. This kind of ventilation scheme always generates a prism-shaped dead space of ventilation close to the ground in between the two neighboring ventilation troughs, causing the grain in this area go moujdy. In this paper a new concept of removing this dead space of ventilation is presented. Positive pressure ventilation and positive-negative pressure ventilation are adopted alternately. Electric current field simulation is used to demonstrate that under different ratios of the distance between two neighboring ventilation troughs to the height of the grain heap the dead space of ventilation can be effectively covered by the airflow field created by positive-negative pressure ventilation .scheme. This new kind of ventilation sheme can be adopted not only in reforming the existing granaries with ventilation troughs but also in designing the ventilation system of future granaries.