In order to obtain the optimal storage conditions of Goji powders at different particle size distribution， differential scanning calorimetry （DSC） and dynamic vapor sorption （DVS） were used to determine glass transition temperature and moisture sorption isotherm， respectively. Moisture sorption isotherms of different Goji powders were of “J” type， it is typical of products with high-sugar contents to show a gradual increase in sorption pattern at low water activities but present a sharp increase at high water activities. GAB model was found to be the best for fitting the experimental data， with average values of R2 （0.9985）， χ2 （3.8988×10-4） and RMSE （6.7153×10-4）. A depression in Tg with increasing water content was observed. For example， when the moisture content （d.b.） of Goji powder （LB1） was increased from 0.133 g/g to 0.530 g/g， the Tg was decreased from 10.82 ℃ to -59.71 ℃. Gordon-Taylor equation also showed good fit for the relationship between moisture content and glass transition temperature （R2>0.93）. State diagrams of different Goji powders were established based on the moisture sorption isotherm and the glass transition curve. Results showed that Goji powders would have good storage stability under the room temperature of 25 ℃ when the moisture content（d.b.） of the LB1~LB4 was below 0.0833 g/g， 0.0906 g/g， 0.0992 g/g and 0.1059 g/g， respectively. This conclusion was further validated by the macro flowability change of Goji powders at 75% relative humidity （RH） for 1 h. The larger particle size distribution， Goji powder showed more obvious caking phenomenon. After exposure to 75% RH for 1 h， all the Goji powders were of rubber state， thereby structure collapse and caking of Goji powders happened. The smaller particle size distribution of Goji powder， more stable of the storage process would be obtained. The results of the present study would provide useful information for the processing and storage of Goji powders.