Abstract: With the help of the hot air penetrating drying test-bed, the influence of direct recovery of waste heat of air exhausted under condition of different air temperature and different air speed on the drying process and energy consumption has been studied and a theoretical analytic model has been made. The test displayed that (1) under conditions of either recovery or no recovery of waste heat of air exhausted, the higher the temperature and the lower the relative moisture of air exhausted. With prolongation of drying time, the higher the air temperature, the faster the temperature of air exhausted rises and the faster the relative moisture of air exhausted falls. If recovery is compared with no recovery of air exhausted, under the recovery of air exhausted and different air temperature , the drying time can be prolonged, the temperature of air exhausted can fall, and the relative moisture can be raised. This will save energy. (2) Whether air exhausted is recoveryed or not, air speed can cause the parameter of air exhausted to be changed, but it is not as obvious as compared with the change of air temperature. The higher the air speed, the higher the temperature and the lower the relative moisture of the air exhausted. If the recovery is compared with no recovery of air exhausted, under the recovery of air exhausted and different air speed, the drying time can be prolonged, the temperature of air exhausted will fall, the relative moisture can be raised. This will save energy. (3) With the help of checking test it has been proved that the theoretical analytic model of direct use of recovery of waste heat of air exhausted is correct. It can be used to predict the parameters of the mixed air conditions in the recovery of air exhausted.