Hey SpiritJZL,
I tried building a game using the plugin this morning for both Windows x86 and Windows x64 in both Development and Shipping configurations and was successful.
For what platform are you packaging? Are you using the C++ installation or the plugin (blueprints) installation? Which version of iTween are you using? We had packaging issues before but they were fixed in v0.8.6d as far as I know. See this post: [Open Beta] Procedural On-the-Fly Animation in UE4: iTween! - Blueprint - Epic Developer Community Forums