Process of drying the pellets in conveyor machine has been considered. Negative role of excessive humidifying has been shown. However, experimental determination of excessive humidifying is difficult. In connection with this, mathematical model of heat transfer parameters of the drying processes has been developed with the use of differential equations. Material balances of moisture transfer in gas and material, the driving mechanism of moisture transfer, heat balance of gas have been taken into account in the model. Parameters of the process have been calculated with the use of the model. This makes it possible to determine regularities in excess humidifying formation.