Abstract: The method of quadratic Dsaturation optimizing design was to probe into the dependence of air resistance on air velocity, grain layer thickness and the flow rate of grain when paddy was flowing in the concurrent and counter flow. The pattern of dynamic air resistance was established by regressive analysis. The dynamic air resistance of grain layer was contrasted and analysed with static one. Single factor experiment was done about the impact of grain moisture. The static theoretical formulation was revised when it is applied to dynamic grain layer. 