Abstract: Sorbitol had four different kinds of crystal forms.Under the different crystallization conditions,the sorbitol which could be obtained were multiple crystal mixture.Due to crystal forms were different in nature,the humidity absorption of multiple crystal mixture was different,specific surface area may indirectly respond in the content of γ-form in sorbitol,so the humidity absorption rate and the humidity absorption percent in multiple crystal mixture of sorbitol were determined on condition of 25 ℃ and 75% humidity absorption.Then its critical relative humidity could be determined by the balance curve of humidity absorption under the humidity condition of 25 ℃.Experiment proved that the critical relative humidity of sorbitol powder is 70.80% when its specific surface area is 0.79 m2/g.In the air humidity was lower than 70%,the humidity absorption of the sorbitol power is little,it is not easily caking and suitable for industrial production.

Key words: sorbitol, specific surface area, humidity absorption, critical relative humidity