► Spray drying is a good technique for retention of bayberry polyphenols. ► We evaluated the polyphenol stability of bayberry powder during storage. ► Spray dried bayberry powder should be stored at less than 25°C and aw of 0.33. ► Anthocyanin in bayberry powder is more readily degraded than other phenolic compounds. Bayberry juice was spray dried with maltodextrin (DE 10) as a carrier and then stored under different temperature and water activities (aw). The retention of the total phenolic content (TPC) and total anthocaynins (ACN) during the drying process were about 96% and 94%, respectively, suggesting spray drying was a satisfactory technique for drying heat sensitive polyphenols. Under an aw of 0.11–0.44, the TPC and ACN in bayberry powders decreased by about 6–8% and 7–27%, respectively, after 6months storage at 4°C; at 25°C for the same storage period the decreases were between 6–9% and 9–37%, respectively, while at 40°C the decreases were in the range 7–37% and 9–94%. The anthocyanin component was more readily degraded relative to other phenolic compounds. The results suggest that bayberry powder should be stored at less than 25°C and aw of 0.33, on account of greater polyphenol stability under such conditions.