The effect of strand geometry and panel density on the rate of gas pressure variation in the aspen orientated strand board(OSB) mat during hot pressing and on the panel permeability were explored.The results of this research demonstrated that the strand thickness has a significant effect on the rate of gas pressure variation,and with the strand thickness increased,the panel permeability also increases.There is no distinct relationship between the strand length and the rate of the gas pressure variation or the panel permeability.The panel density has a very important effect on the rate of the gas pressure variation and the panel permeability.As panel permeability increased the water absorption(WA) of panel will increase.This research results are beneficial to further understand the effect of aspen OSB manufacturing parameters to mass transfer during hot pressing and panel properties.