During heat pump drying (HPD) of Penaeus vannamei meat physical and chemical changes are destined to occur which result in a decreased quality attributes. However, the mechanism of quality degradation was not explicated. The gravimetric method and differential scanning calorimetry were employed to investigate the moisture desorption isotherm and the glass transition temperature (Tg) of Penaeus vannamei meat, respectively. GAB model and Gordon—Taylor equation were selected to fit the experimental data of desorption isotherm and Tg, respectively. Penaeus vannamei meat was dehydrated at 35℃ and 1.5m/s air velocity by using HPD. The quality attributes (such as hardness, toughness, shrinkage, total color difference and astaxanthin content) were analyzed at time interval of 1.0h during HPD. The mechanism of quality degradation was explicated based on glass transition theory. The results showed that at the present drying conditions, Penaeus vannamei meat sample was in a rubbery state, characterized by a great mobility and remained this state until the end of drying process. The quality attributes were changed as drying continued, which can be related to the rubbery state of matrix during HPD.