Research on vacuum infrared radiation drying of Rehmanniae was carried out u sing an improved vacuum infrared radiation dryer. By means of logarithm of experimen tal data and linear regression, the pattern of thinlayer vacuum infrared dryin g model of Rehmanniae, which was related to the temperature of radiation boa rd a nd pressure in the chamber, was set as Modified Page equation, and the expressio n and values of model parameters were also obtained subsequently. The model coul d describe and predict change regulation of moisture ratio very well according t o the comparison of experimental values and calculated values.