To solve the problem of apple powder strong hygroscopicity, wheat gluten was selected as a natural anticaking agent and added into apple powder in different proportions. The moisture absorption data of the samples was monitored in different relative humidity environments at 25 °C and 35 °C. The results showed that the addition of wheat gluten could reduce the equilibrium moisture content and the size and number of agglomerates of freeze-dried apple powder. The fitting parameters of the Guggenheim-Anderson-DeBoer and the low-field nuclear magnetic resonance results revealed that the existence of wheat gluten restricted the water migration, which was conducive to maintain a good particle state of powder. To sum up, the wheat gluten as an anticaking agent could not only have the effect of inhibiting moisture absorption during the storage of freeze-dried apple powder, but also possess the potential to be used in various fruit powder production.