The effect of the drying properties on hot air drying by relative humidity control of Chinese yam was studied. The test material was treated with high humidity after the hot air drying, and factors on the drying characteristics and rehydration characteristics were investigated, including the treatment time of humidity, slice thickness, dying temperature, and drying air velocity. The L9(3⁴) orthogonal test was used to get the best drying process parameters on energy consumption. the content of polysaccharide and the color of two kind of yam (prepared by the best drying process parameters on energy consumption and hot air drying without relative humidity) were determined. The results showed that, compared with direct hot air dying, high relative humidity control could not only greatly shorten the drying time, but also improve the rehydration characteristics. Moreover, the energy consumption was the minimum of 19 056 kJ/kg·H2O when material under the conditions of constant temperature and humidity ( Slice thickness of 3 mm, temperature of 60 ℃, relative humidity 40%, treat time 30 min), hot air drying treatment (air temperature of 60 ℃, air velocity of 3.5 m/s). Under this condition the ΔE value of yam chip and polysaccharide content were 8.17% and 5.14%, respectively, while those of directly hot-drying were 12.35% and 4.96%.