In this paper, a series of paddy drying experiments were conducted on a deep fixed-bed and we investigated the effect rules of five influencing parameters on drying time of paddy. By using the quadratic orthogonal rotation combination design, the nonlinear function between the drying time and the five influencing parameters are built up. Then a detailed study of the qualitative and quantitative effect rules of each influencing factor is elaborated. The results of this paper conclude the rules of how drying parameters influencing the dry time of paddy. And also, it reveals how to reduce paddy drying time and improve the productivity, which have significance in practical productions.