Abstract: The study describes a construction of a new batch cereal grain drying machine. The machine operation is based on combined drying consisting in infrared heating at the ambient pressure in vacuum. Then grain is dried by the convective method and cooled by the ambient air flow when grain is discharged from the drying chamber. Experimental studies proved that the highest possible temperature of barley grain heating that doesn’t result in protein denaturation is 70°C. There is a regression dependence of moisture removal on preheating and vacuum heating time, vacuum volume and the initial moisture content of barley grain resulted from the Box-Behnken second-order design for four factors. Mathematical models of drying mode optimization are developed. Parameters of a barley seed drying mode are found when solving the problem of energy cost optimization and average drying rate. Barley grain drying enhancement is found to be achieved by cutting operating costs and increasing vacuum volume.